If you're worried about holding the pull bouy, you can always use a strap to hold your legs together (around your knees). That's what my BIL does, he has parapelegia. But I really don't think that holding the pull bouy will bother you. It involves mostly your adductor muscle group, not your quad and it might even help a bit.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS