An SKS can be run, but it is not a great option for tac rifle/multigun... I've seen some guys VERY fast with stripper clips, but they still get left in the dust on mag changes, especially when you start talking about using LAR15/XCR pistol mags.
I run tac rifle and multigun matches in GVRD and Fraser Valley, and the Vz has all but disappeared from the sporting landscape. I think there are a number of reasons: there are few great RDS/scope mounting options, the mag changes are slower no matter how much you practice your Spetznatz mag changes, and there are no good pistol mag options.
7.62x39 ARs are a poor choice IMHO... I use one for practice, but not for competition. I had to put heavy hammer springs in my x39 AR to ensure it would shoot hard milsurp primers. This makes the trigger pull HEAVY, certainly much heavier than the Geisselle SSA-E I have in my 5.56mm AR I generally use. There is also noticeably more recoil with x39, so my double-taps open up from almost touching to 3-4 inch spread.
The XCR-L is the only x39 rifles that perform well at tac matches, though it seems as the ones that run well are great, and the ones that don't are terrible.
YMMV