Just a thought, my solution was to take the easy way out and use existing parts of boat by putting a 2 fold purchase on the back stay and 2 x ring bolts in the transom plus a webbing sling and plastic rollers over ladder (on my boat.)
I have had this for 9 years and it works fine, my wife can pull it up and i use it for engine lowering and hoist. if I am transiting in bad weather I take the dinghy in and stow it under forward bunk through hatch I put in it.
See photos, hope this helps
Odysseus
Bad 38