I don't know about questionable. Alot of anti-SERPA hype is based on 2 cases of AD that everyone knows 100% was caused solely by the SERPA, and nothing else like finger control.
God knows there has never been any other ADs before the SERPA came along. Not like I'm arguing with you here, but I never buy into the "this is all bad" crap about anything, holsters is just one thing.
I've had a SERPAs for a couple years now, and some local guys have been using them longer than that. Besides, for airsoft, there are a thousand bozos who could do a thousand things to cause an AD, the last thing you need to worry about is the holster.