Hi everyone, I found this thread a couple of days ago and finally finished reading it. I have been a sprint 2 owner for several years now, but recently I've decided to give the car a try on the race track. Awesome job to everyone who contributed to the thread; it has been a big help to me getting my S2 up to par.
I wanted to share a little mod of my own that I figured out to make the battery holder in the S2 larger and simplify it. This mod allows the S2 to fit up to 25mm lipo packs with no issues. This mod does also require the belt lift mod(post #2) if you want to use 25mm batts.

Only one Part required: Tekno TKR40007K (or any velcro strap set close to 10.5in)

Mod is pretty self explanatory from the pics.
1- Remove stock battery clamps.
2- Wrap strap around aluminum post in front of battery holder and pass strap through its loop.
3- Wrap strap around plastic rear post and velcro it together.