Sorry for continuing with this..
Was advised to capsize with sails up, but waiting for winter to do an overhaul on the cat, rudders, seal mast etc. My cat turns turtle at the drop of a hat, to me recovering from turtle is the easy part. So yes no main in place it will stay turtle.
Tried dropping main in 5 - 10 knots, easy, but could see main would be blown off, so suggest using jib car ropes to tie main to boom, also to try keep boom in mast on swivel, retighten downhaul. May as well throw an anchor down as speed etc is drastically reduced.
The treading water bit was easy but cat kept on running me over.....
What stresses would the mast have running on jib alone, with many powerboats on dam creating waves, causing mast to swing back and forth during lulls.
Amazing to think this machine was designed without CAD etc.
Thanks