Had the TPA pulled from my child today.  The expansion from it was okayish.  I will know more in the months ahead.  I'm blessed to have landed into this knowledge.  I prefer a highly arched palate to drop (braces can do this okayish, but sometimes it leaves the gum mounds behind.... as it is less skeletal).  An example of this is here: https://ormco.com/products/damon-system/studies/freedom.php   Dropping a high palate helps with airway.  Additionally, the other trick is that true skeletal expansion can also widen the nasal cavity, thereby reducing that child's chance of problems resulting from nasal allergies.  So, I wanted to do a tiny bit of RPE.  In the end.. I think that I stumbled on the optimal solution.  However, nothing on the market fits it exactly.  May need to create something new?  Anyway, the closest thing to what I think would work well is a wireframe DNA appliance.  However, I just couldn't find anyone qualified who was willing to do it.  So... I did a Schwartz and SHAVED IT DOWN.  This was done with a white chocolate kit kat bar (in lieu of denture spray).  It tastes better, too (unless you don't like white chocolate ;-).  You're going to get true palatal expansion in a kid... trust me.. it's scary how much the face flops around for 8/9.  Freaky.  True cheekbone expansion, etc.  Very nice look, but in my opinion, a y-shaped is the way to go.  Even if you don't need any forward movement, I like having the incisors left out of the equation, but the forward part of the maxilla supported.  It obviously depends on the kid, but with the incisors pushed out, the bridge of the nose got really wide/manly looking.  I tell you, it's scary!   As for the anterior (forward) part of the maxilla, I often have seen this drop with RPE... and I'm not the only one who notices this.  The issue that I took with the Schwartz was that it got lost and all progress quicky evaporated...even in 2 weeks.  So... that was annoying.  I strongly suggest getting 2 exact ones as a time.  That way, if one gets lost, you'll have an instantaneous backup.  But the problem with it was that the teeth tipped out a bit.   I think that could have been mitigated with an Adam clamp.  Additionally, a fixed appliance may be beneficial (such as a Crozat or alf).  The DNA wireframe has a lot of similar attributes to the Crozat (besides being removeable).  The Crozat was designed for facial aesthetics decades ago.  Then they got the turn-key styles in.  The issue with that is there isn't even, continuous pressure.  The issue is that generally speaking, the more intermittant you turn, the less the body adapts.  The less the body adapts, the less natural the look.  People are starting to be educated and realize what orthodontics does to the face.  Truthfully, the MOST natural intervention is the most attractive.  That is what I've been primarily interested in.   That and airway.  A diet DOES change the faces of kids.  A crunchier diet shortens the face wheras a softer diet lengthens it.  I don't believe it doing a bunch of crunchy things, though, because you want to widen the palate before raising it so it doesn't cut into the precious nasal cavity area.