I'm totally confused by what you are saying. Weight is not a factor. The only purpose for your toplink is for lifting the rear wheel of the cutter for transport, otherwise it serves no function, only restricts the up/down movement of the cutter in your case. Your rear wheels totally support the rear of the mower and your lower lift arms support the front. Your toplink does nothing. (EDIT), I should add, the toplink does obviously limit the in/out movement of your driveshaft in extreme movements.