I put a 22lb spring in, first thing. I dont switch out, even when shooting lighter loads. I rarely, if ever, have any kind of FTFs. My advice is, if you're planning on running hot loads, put a heavier spring in, and forget about it until 5-6K rounds when its time to replace it.

I've got a G29 Gen4.
The only changes I made were ext slide release, night sights, pearce +0 extenders, and a pyramid fulcrum trigger.

I don't intend to shoot underwater, so the maritime cups weren't needed. I don't need a $13 part to help me take down the slide, its not like I do this all the time. my 29 is my carry gun, I carry low profile, so no G20 mags w/grips. If I'm at the point I am putting a 15 rounder in, the last thing I want to worry about is if an external part is causing the mag to not sit properly. The pyramid will probably raise some questions, but the fact is I got it on sale for $130 (this is for the middle kit), and it eliminates all pretravel as well as reduces reset greatly. Once you try it, you will never go back to the stock, or even ghost connector trigger bars.
I have a heavier spring on my fullsize G20, but the 29 shoots everything in it without an issue, even underwood 180gr.

As far as other barrels, I have shot .40 out of the stock barrel. I'm not advocating anyone do this (do so at your own risk), but I can say that I have shot 150 rounds through both guns, and not one single issue whatsoever. I wasn't going to spend $120 on a barrel, when I can spend that on ammo. I still carry with 10, I just practice with .40.

I'm really new to this forum, are people having problems with factory PPU, or just reloads on their cases?
I dont have any left, but if its that much of an issue, I won't be considering it an option in a pinch anymore!

Both of my Glock 10mm's function extremely well.

Gen3 G20, wolf 3.5# connector, 22-4lb (I can't remember which, sorry!) brass stacker return spring, extended slide stop/release lever, night sights, but everything else is stock.  Bought this August 2013. This eats everything. I typically feed it Armscor when I can get it, or Underwood when they have it in stock. I've used PBR, PPU in a pinch, and the Federal red box once. Every once in a blue moon I have a FTFeed, but almost always that has been a function of ammo seating improperly. I have put over 3000 rounds through this since last August.

Gen4 G29, stock except pearce grips and triji HDs. Bought this March 2014. I've probably only put 3-400 rounds through this, so in my opinion the jury is still out. It has only had Underwood 180/165, Armscor, and PBR 165 FMJ.  Hasn't had any issues yet.

From what I gather on this topic, I am extremely lucky here?

I've been lurking on this site for a while, even though I have had a Gen3 G20Sf since August 2013. I bought a Gen4 G29 (nonSF) about a month ago for EDC use. the 20sf is pretty stock except ext slide release lever, 3.5 connector, and some NS. the 29 is stock except for NS.

I've been a fan of the 10mm for a long time, at least 20 years. I dont really know for sure what started it. I just know I am addicted to it. I suppose my next 10mm will be a STI perfect 10, but that seems a few years off.