Howdy folks

Just treated myself to a pair of DHB Compression tights, £29 off Wiggle=BARGAIN!!!!
(Just couldn't afford/justify Skins).
My ridiculous question of the day is.....
Just how tight should the buggers be, to be of best effect.
My problem is that I'm between sizes.
Too tall for a medium, too skinny for a large.
The mediums are crazily tight, the large feel like a pair of tracksters!
Opting for the Medium.
Any users out there have any opinions on this matter??????