I’m wary of doing the armpit type hold as the brachial plexus can be vulnerable in this area, but thats just me being a scaredy cat as I’ve had arm nervy problems in the past. Not really sure about arterial routes though, is there a particular reason why you are more worried about arteries? There are loads of people that do these moves with no problem, and there are loads of people that do much more simple moves that end up injuring themselves, I guess you jsut have to weigh up whether you want to take the risk.