Per Don Y:
A risk, here, is the stresses that would be placed on the "holes" would
differ from what they were designed to expect. I assume this would
crack some bit of plastic (?)

Good catch....

I put something like that to a Hobie rep a few weeks ago and his reply
contained the phrase "...think breaker bar...." so I dropped the idea of
messing with anything that goes into those holes.... the downside is
just too severe.


Then, make a fork that clips onto the
cross member of those wheels and extends forward to a point at which
a "pivoting wheel" is mounted.

I.e., the fork is triangular in shape (like an old wooden "crutch").
At the tip, a pivoting beach wheel is mounted facing downwards.

That is pretty much what I had in mind - but was looking for some
off-the-shelf source for the pivoting wheel.
--
Pete Cresswell