I installed a T-Lock feedneck from trinitypaintball.com.
It works perfectly and means one less hex wrench for the SP-1. Design and quality are better than expected based on the picture. Locking arm can be rotated to accomodate any loader shape. My Empire Reloader (must be sanded-down for many feed necks) fit without any problem.
Note: I got a better price and lower shipping cost on e-bay...
See a picture of this locking feed neck at: