I agree with the above poster re forgetting about trying to look cool. Having a high strap makes things a lot easier for technical playing. Most jazz players do it this way too - for technical metal players using this method check out Cynic. Another good trick is to wear a strap when you are sitting down so your guitar is always at the same height (of course this doesn't work if you play with the guitar on your shins!). Hand size shouldnt come in to it either, just work out a way that works for you. Most of the good players out there have their own unique way of fretting, if you can't sweep arpeggios over 6 strings then try playing them differently. Also, there are lots of ways (shapes and fret positions) of sweeping the same group of notes, just find the same note at a different position on the neck and work from there.