If you do decide to use the stabilizers to attach the jack wheel, make sure you have the tires ( both sides ) chocked front and back.
This is good advice if the garage floor is anything other than completely level, and would also apply with any other method of holding the tongue up while adding the jack wheel, such as blocks or jack stands.
To continue the question of “lifting” with the stabilizers (not that one should, just for discussion sake) isn’t the real problem flexing the fiberglass more than bending the frame?