hi bobby;
nice boat! please bear with me as i try to explain my system. it worked really well on my s&g guillemot, two weeks ago.
my grab loop holes are 1/2". i used steel 'cause it's my job. from 1x1x1/8 angle i built a U shaped bracket with a round pipe off the bottem. drilled through the legs of the U neer the ends to accept a 1/2" rod. the pipe on the U fits through a pipe welded to a bracket mounted on a stand/sawhorse. holes drilled through both pipes to lock in position upright or inverted by inserting a bolt. the pipe from the U extends past the end of the sawhorse pipe and has a hole drilled through to accept the "spinning handle" back to the 1/2" rod...cotter pin holes drilled at the ends to keep the rod on the U. more cotter pin holes to keep the kayak in the middle of the rod. i made wood washers from plywood to gaurd the 'yak while spinning. i wish i could post pics, it's so simple!
best regards;
daren.....