beryl george wrote:

Wouldn't it be simpler just to run ropes from the bottom
corners of the cradle frame to strong points on deck?

Would not rope stretch be a possible potential problem with
such a heavy boat.

Not really, but you could use chain instead if it worries you.

Just roughly: Suppose your mast ropes are at 45 degrees, the
deck is 10ft above ground, the mast is 50ft tall, then the
mast ropes will be 85ft long.

Suppose a lateral force is applied (by wind, say) which is enough
to tilt the boat by 5 degrees against the tension of the mast
rope. That would cause the mast rope to stretch by 3.5 feet, or
about 4% of its length.

If your half-beam is 7ft, and the cradle bottom half-beam is
the same, I calculate the cradle rope would need to stretch from
10ft to 10.6 ft, or 6% of its length, in order to permit the
same 5 degree angle of heel.

Now if you were using the same type of rope for cradle-to-deck
as for elsewhere-to-mast, and if both ropes may be presumed to
be operating within their linear stretch/tension range, then it
takes 1.5 times as much force to stretch it by 6% as by 4%. The
lever arm advantage follows from the stretch distance ratios,
3.5:0.6, or about 5.8:1. This means that a heeling moment which
exerts 1 unit of tension on the mast rope would exert 5.8 units on
a cradle rope. Divide this by the force ratio of 1.5 to get a
number a little less than 4. I reckon that means you're as OK
if you use 4 cradle ropes each side as you would be if using one
mast rope of the same calibre and stretchiness each side.

Better still if you use heavier and/or less stretchy rope.