Could you possible use these and make a rolling frame underneath them to mount on? That would mean you could make them any height you want. Just use strong material for the base these would mount on. Maybe a solid piece of a butcher block counter table so it could hold the weight since it won't be setting on dirt or concrete?
We used this on our duck pontoon boat before we got a trailer for it, but as you said, your sea legs will probably be too low.
The only thing I was told my our mechanic is that you want to center them under the nose cone weld and the back end cap weld or you could "fish hook" a log (meaning it would bend)..
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