I am not sold or convinced using a toppping lift is an ideal solution. Our topping lift is in use and supports the boom. Are your saying your topping lift is useless on your boat? Not sure I would want that strain on my mast on the angle from the top, or the added force transferred up high as the weight of the dinghy
was held by a point 50 ft above the deck. . If you were going to use a topping lift, why not use a secondary halyard instead.
On thing I noticed is that you dont have a cross piece beween the two arms. What keeps them from rotation and moving . What keeps the center of gravity equally between the two arms? Instead of the weight of the dinghy
directly under each arm it looks like it is hung like a pendulum under the davits. That would increase the swing potential. I know on some of those huge transom boats like Benes, Hunter and Cats That may interfer with the swim platform. Thats why usually the have their davits imbedded in their hull and not the transoms.
I looked at the removable ones and that plus the lack of lower support pushed me to fixed davits. This may also help prevent " flexing" and movement. To me most of the forces should be applied lower than higher on davits and the removable ones all had the pressure poisnts up high and depended on the rear rails for support to much. The Garhauer davits we have came in two styles. either they go through the hull and are bedded on a plate on the hull. Or they are bedded on the trasome with a huge backing plate. This way the forces are spread out.
Also what are your attachment points. Do you have web starpping which comes to a stainless O ring or are using "line". It appears its line
and does the line
have a stretch component.
I looked at the forces not just the weight I was asking the davits to carry. As you boat pitches and swats in the wave action the forces of the dinghy
/ motor will be many times more than just the weight of both and they are transferred to wherever you have attached them to you boat. It is important to spread those forces out a wide as possible and as low as possible on the boat.
The 11/4" stainless Garhauer davits we have are rated at 250 lbs per arm. Thats dead hanging weight.