Can anyone forbid me from using roof beams for small boats?

Hello together, I intend to build a railing carrier myself for a small light fishing boat of approx. 2.5m and 40 kilos of weight, which fits on the railing of the Omega B Caravan. So basically two simple struts, which go from the left to the right railing part, which I can clamp to the railing and then back up to my boat. Actually, as you can buy it, just adjusted to the boat. Only, can I use it so easily or is there only a purchased one with ABE? A over muchleich also someone has something suitable at home in the basement….should not be expensive and offer an edition of at least 1.3 m…..the boat itself has 1.2 m