@Mike_Ward
Allowing a waitlist and making the waitlisted folks pay goes against the waitlist idea and most shooters would push back against that.
But, if that’s the way you want to go then, What I would do is this.
Set up squad sizes to what you want it to be.
Do not turn on waitlisting
Check the require full payment box to make everyone pay.
Check Require payment and approval to squad.
THEN you have to go down the approve/view list and physically approve the maximum number of shooters to fill the match. (two mouse clicks per) Starting with registrant #1.
Now you have other shooters who are not approved (and cannot squad) but have paid sitting in your queue.
If someone drops out you refund them then remove them from the match and approve the next paid shooter.
The only thing you will have to do is manage having shooters who have given you money and may not be happy about that and not getting in the match.
AFTER the match you refund all the shooters that didn’t get in. 
That’s about the only way I can think of to do this.