If you chrono, and find you put your velocity adjuster all the way in and still can't get under 300 fps, you will need to:
a. Get a low pressure tank
b. Do the mini-reg mod to make it compatible with HP
c. Get a cp vertical ASA adapter and a new reg.
Considering option B is free, I'd take that route.
You may very well be fine. I have 2 A1's, both work fine with HP out of the box (although I'd be in trouble if I needed to play reball).