The L6 should work in the SP1 with the SP1's own bolt stop. It's only the L7 that needs a special bolt stop.
Although, you could probably make a few bucks by selling that L6 to an eNMEy owner (since the SP1 has a solenoid to control dwell it doesn't need a bolt with dual tail o-rings to function like the eNMEy does) and then use that money to buy an L7 or a Deadlywind Hollowpoint bolt.
If you're going to stick with the L6 or even the L7, the only other upgrade I'd recommend is a 360 QEV from GOG if you don't have one already. The Hollowpoint really doesn't need a QEV as it's forward speed is already ridiculously fast.