Well, I've been playing MR4 again. And despite everything I've tried, none of the monsters seem to be able to get above a +27 on any level 2 or 3 gadget it seems. Is there an advantage at all to use the level 3 gadgets or am I doing something wrong?
Does the stat increase just simply cap out and its a sign I should move up to level 4 gadgets?
I have been training with all sorts of magic and healing things... Right now I have a Magic Book, a Magic Flying Target, a Healing Rock, and a Healing Pitching Mac... As well as the Spa (special level LIF, which should increase in difficultly with the monsters level).
Is there a reason why it seems to cap out at +27 at 100% on both levels of training?
Any advice?

Oh, and I should add that I was also getting +27 on the level 2 gadgets that had no enhancement effect. All with the wind drum.

I'm partially developing a theory that wind drum has a detrimit to it we're not considering. I had an alternate game that I created and one that I didn't use the wind drum at all, and the monsters ended up with overall better stats.
Sorry I keep adding to this, I keep forgetting things. I'll look into this though when I go back to playing it. (busy with school right now)

I haven't played enough recently to comment on many training specifics, but I do know that at the peak of MR4's popularity, it was generally recommended that ranchers stick to modified Level 2 and Level 4 gadgets for optimal results.

Level 3 gadgets just don't have a worthwhile upside to my memory.

Yeah, I've got plenty of Tough Hearts.
That's 'cause whenever I go out to Kawrea I get plenty of combonation items but never any medals.
I can hardly go to any of the + dungeons, but that reminds me...
I was gonna ask, are the rates for finding medals more common in + dungeons?
I'm mostly looking for opinions though.

I have gotten my monsters as high as 30 on the level 2 gadgets, and in the primary gained stat on the level 4 gadgets, but only if it's a stat in which the monster has a high racial gain rate.

For example, in my first game, I had a Mandrake (Plant/Dragon) named Ming, who was in his prime. At the time my only medal-augmented gadget was a Magic Trampoline. I had five level 2 gadgets on my ranch--the Magic Trampoline, the Sandbag, the Life Blade, the Tub, and the Target--and one level 4 gadget, the Phonograph, which I placed to take advantage of all five monsters' high Intelligence scores. I also had two Wind Drums, placed so that all of my gadgets were in the effect range.

When Ming was in his prime (shortly after I received the message that he had become very mature, and I must adjust my raising to keep up with him), I trained him on the Phonograph. He was at full energy, and had been fed the week before. My raising policy was Lenient then, so he rarely got stressed or frustrated. When I trained him on the Phonograph, he achieved +30 to Int. and +14 to Lif. I do not remember how much Defense he lost, sorry, but I think the loss was two or three points.

Ming got +30 on the Phonograph three times while he was in his prime. Each time he got the +30, he had been fed and rested the week before, and had not been stressed out. If he trained on the Phonograph in less ideal conditions than those described above, he got +24 or +27 to Int., +12 or +13 on Lif., and -3 to Def.

I attributed that gain to several concordant points:
1) Ming was in his prime. The trials took place beginning immediately after I received Ming's maturity notice, and ended after Ming began to get "pretty old."
2) In each incidence of the +30, Ming had been rested and fed the week before.
3) Ming led a low-stress life.
4) The Wind Drum was in place.
5) Plants tend to be high gainers in Intelligence.
6) Ming's non-Plant parent had been a Dragon. I'm not sure if this had to do with Ming's success, but I'm also not sure that it didn't. Dragons are also high gainers in Intelligence, so I felt it was worth pointing out.
7) One more thing. I am not sure if this matters at all, and I doubt that it does, but I was a rank S breeder at the time of Ming's Phonograph successes, and had already finished the game's main story.

In the same game, after Ming's successes, I raised a BattleRocks (Golem/Durahan) named Harvey, to see if the +30 experiment could be made to work with a level 2 gadget, as well. Under conditions identical to those I described above, Harvey got +30 to his Pow. on a Sandbag in four successful trials. The Sandbag had not been augmented with any medals, but it was in the effect range of the Wind Drum. Again, his trial conditions matched those described above for Ming exactly.

On a tangential note, does anyone else reward monsters for 100% in training? If my monsters get 100% on training, I give them a favorite toy, and it honestly seems to help. Has anyone else tried this? If so, what were your results? I am going to try and make up a more scientific way of determining whether there are any benefits to rewarding for perfect achievement.

Every time my monsters train aat 100% I give them their favorite
toy, favorite food (if hungry), and a praise. Most of my monsters
seen to train well.

Answering the first question I've had a Zuum/??? that I put on a
healing trampoline and he gained +35. Also I have a Ripper/???
that trained +31 on a target with no medals added. My Garu
though has not trained higher than a +29. Yes, I only have 3
monsters even though I'm an S Rank Breeder. The other
monsters just took up space.