I'm trying it tonight!
I suspect less than total success as it can only be moved in one axis (side-side), however a small ball head tripod head or an x/y guidescope bracket could be used.
The main problem, as I see it, is the size of the spotting scope.
Mine (a Celstron Regal 80ED) is about 2kg. That's pretty hefty for a finder.
I don't see the point in going much lower in aperture (unless you want it to double-up for widefield and terrestrial viewing as well) as there are excellent finderscopes in the 50-80mm range that are half the price and 1/4 the weight.
But...
We'll see how she goes.
