A 70 mm stem is very very short. Sorry Don but the stem length is NOT suited for all types of riding. It is however good for DH or jumping.
Most companies will overlook other frame damage to cover a specific warranty issue.
The reality with warranty is that your dealer is (or isn't) your advocate in the warranty process. The dealer holds the cards here. If you have the dealer who sold you the bike process the claim, your chances are much better than if you go it alone or with a random shop.
Painting any bike pretty much voids any and all chances of a warranty in the future.
Good luck.
I was just going by what I've riden and learned over the years. BITD, I ran those long ass 130mm stems w/ friggen bar ends. On that same bike ('97 Rhygin), I'm now running a 100mm Thomson. Mind you that bike is a pretty stict SS XC build with no jumping going on.
And I think a 50mm stem is spot on for jumping and DH. I'd feel really weird with a 70mm stem on my DJ bike and do swap in a 50mm on my sussy rig if I know I'm hitting drops and stuff.
For a all around trail bike I still think a 70mm stem is a great size. I rode last week (and over the past 5 or so years) with some of the best all around riders I've ever seen up in VT. I noticed years ago they all ran shorter stems, higher rised bars and bunch of spacers between the stem and headset. Ask mergs - those guys kick some ass up and down hill. The shorter stem length doesn't seem to slow them down.
There is also Lee's writeup:
http://www.leelikesbikes.com/stem-lengthrise-for-a-trail-bike.html
It's unfortunate about the painting of bikes voiding warranties but I can see why. Prepping and powdercoating could do damage in the wrong hands. The guys at Sinister said they would be fine if I had a local powdercoater do my GRUITR frame. And I've seen Turner still help folks out even with repaints so there are a few companies that will still stand by their product.
Another thing worth mentioning about a repaint is the cost for a proper job. A powder coater will charge about $100+ for a frame. Add the time or cost for a tear down and rebuild, plus stickers and it can get expensive - maybe even more than the frame is worth.
I like having one-off colors and builds myself and don't mind dealing with the issues and actually enjoy the project.