It is not the riser covers you should be concerned with. What the big problem is, is with the main container closing flap. In a sit they will almost certainly come open. I had two premature deployments because of that flap coming open and the bridle catching air, thus deploying my main. Luckilly, I had a BOC and it just pulled out my pilot chute. A horseshoe would have really sucked. The "fix" for a vector II is to cut off the stock tuck tab and replace it with "walrus teeth" at least two inches long. I never had a problem with mine after I did that.
Velcro works great for free-flying provided it is properly maintained. Replace pile Velcro every 200 jumps and replace hook Velcro every 600 jumps. Keep your main closing loop tight. Hint, if you can pick up your rig by the main bridle, the loop is too tight. Another option for the main pin cover tuck tab would be installing a shark's fin similar to those on Reflexes and Sidewinders. I have retrofitted shark's fins to several Sidewinders, but have not tried it on a Vector yet. Just be sure that your local master Rigger understands tuck tabs before he does the modification, or heaven forbid, you could even phone the factory!