by any remote chance would the yakima rack fit between the glass brackets? then you could use a pin front and back of the rack possibly thru existing holes.

if not, would the rack fit on top of the bracket or below? using the same pins or maybe bolts. if bracket is just one flange, add another above or below?

if the yak is just for yr self(so adjusmt not an issue), maybe larger rotating footrests(make them or kayaksport) would make comfort using yr pipe as an axis. attach rudder line to toes.