In my experience at Wannaplay you'll be fine if you simply set it to semi, just don't put it on full-auto. Unless you have a response trigger, I don't know that there's much you can do to keep one of those from kicking in.
That being said in five years I've never seen any walk-on player get stopped by a referee and have their marker checked for R.O.F. or fire mode at ANY field. Except tournaments of course, I think those are monitored pretty closely...
As far as why, I think there's a couple reasons to try to limit the rate of fire:
1. There's always some young kids there, first timers, that might not be down with getting hit five times consecutively, that might ruin their day. And nobody wants unhappy customers, right?
2. Masks can only take so much of a beating, especially at close range. If someone's wearing a cheap P.O.S. mask and takes five in the lens at close range there's going to be a serious safety issue.
In my humble opinion the whole "
semi-auto" rule is getting stretched a bit thin. Most of the lower-end electropneumatic markers are capable of hitting 15 balls per second in semi-auto mode with just a little bit of practice, who knows where the high-end electropneumatics are now... 25 or 30? That's just insane.
My point is that
full-auto is typically capped by the marker manufacturer at 8-15 bps and people are sometimes almost doubling that in
semi auto mode (with enough practice of course). So the people that
are compliant with the semi-auto rule may be firing MUCH faster than those who may not be compliant. Know what I mean? I can't tell you how many times I've seen it happen, heck, I've even done it myself a couple times.
My suggestion for a solution: Force everyone to use gravity fed hoppers.

That'll take 'em down a couple notches.
