I have a half-zip Denison from SOF.
With no extra poppers on the back to get it out of the way, how does one stop the crotch strap waving about behind?
Safety pin?
Attach it to the poppers on the side? I have seen thos done before.
Any way you like! Cut it off, or as DT suggests use the side adjuster popper, safety pin, a few stitches - whatever...
I'm afraid I'm a dangler too. I often clip it to one side but in the rough and tumble it always unpops and flops behind me.
Wait - am I on the right forum? 
Just attach it to the poppers on the front, where it's intended.
I do, and you get the added bonus of a bit of protection in the important area.
Before I bought my Denison I checked on here as was advised by Yith to make sure I get it a little oversize. As a result, I can wear it buttoned in and it rarely pops out and, I am happy to say, has yet to cause groinal discomfort while prone or crawling.
Friends meet to part - love laughs at faith;
True foes, once met, are joined 'til death!
Yeah, i found it practically impossible to wear done up 'correctly', it's unpleasantly like wearing a nappy.
Ahem, allegedly.