RE: bolt length questions
I'm guessing you are kinda new at xbows, so if not, please don't feel offended. The b-heads you posted the link to have some terrible test results in two places that I can think of. You can either do your own tests, read the tests others have posted, or try the tried and true stuff the guys here use. Most importantly, you have to see how what ever you choose works on yourbow/arrow combination. What works for one setup doesn't always hold true for the next guys. I never meant to imply you would get over 300 fps outta a Viper, just what arrow changes does to what velocity you are getting now. I think you added fps instead of subtracting. And, that only applies to MY carbons, they all are different.
Edited to add: I just googled your bow, it's 165# pull, but no info on the weight of those 17" arrows. You really need to know that soyou know the minimum weight you can go to, or like Hotburn said earlier, possible partial dry fire. Once you know the weight you can calculate what changes [heavier] will do to your ADVERTSED fps. Hope this helps ya some!!