It does cut some circulation off, depends how tight you go. for me the velcro method works fairly well and i dont have to yank on it if you know what i mean and squeeze my shaft really tight to prevent slip, i go tight but i dont go crazy on it.
and i can wear it 1-2 hours straight like this when i want to and i dont get a cold end or anything like that, which does happen when you strap in too tight.
infact usually its my shaft thats feelin it before anything else and i take a break at 1hr usually ( i wear it at 1200 tension )
im a noob but ive been using the
SG now for a fortnight straight, 5-6 hrs per day with the velcro, no slippage.
i think perhaps too much wrap with the velcro is no good, i just use the foam tube that came with the
SG, and the velcro grips under my glans because glans is larger than the shaft, and the velcro cant slide over.
I feel with too much wrap it begins to work its way up the glans because you lose that 'edge' where it stops under the glans, too much wrap smooths it out, and you end up having to strap in tighter than you do with less wrap.
thats my experience with it so far anyway, i know everyone is different though, including what they can tolerate on their dick, so you just have to experiment and find what works for you.