There were three models of spaceguns, as I remember: the 15-pin dual-gun gameport model, a USB single-gun VGA model, and a USB single or dual gun TV model. Your spaceguns have the 15-pin connector?
Nope, mine are USB.
Ah, the GS guns, the subject of this post, were the game port guns. It's been know the two USB models work in 9x. (Mine do, too.)
And FWIW, the "USB single-gun VGA model" has been doing dual (or three) in official mame for a while now. In both XP and 9x, but not 2000. (Do
not use the -dual_lightgun option, though; that hack was specifically for the TV "dual" guns.)