I don't have ( yet ) a shorty .22, but I do have a 16 1/2" .44 mag. You will not loose anyvelocity fromthe shorter barrel, and in fact, may well gain a few fps, as the .22 long rifle round optimizes in about 14", according to much that I have read. Much longer, and velocity is lost due to bullet friction in longer barrel.
Accuracy should not be affected for the worse, and may in fact be better in the short barrel. The sportster uses a somewhat light barrel, and cutting it shorter may well tame down what little harmonics it has. I assume you are going to scope it?? If you decide to use open sites, and go through the trouble of putting on a proper height front site, you may not be able to shoot it as accurately as open sites on a full-lenght barrel, due to sight radius. But that has to do to shooters ability, not weapons accuracy.
On my shorty, I used the synthetic forearm that is held in place by a round knob, about the size of a quarter or so. I think it is the "survivor" forarm. It makes it a tool-less, quick job of taking it down, and carrying it in a very compact case. In addition, the sling stud is on the exteme front, so when it is slung over the shoulder, very little barrel protrudes upward, making it pretty much snag-free.
Mark