Sometimes you will encounter a padeye whose width physically fits inside the clevis but is simply too tall for the body of the tester.
If this occurs simply pack ethier side of the padeye with pieces of steel plate or hard-wood to provide a surface with the desired height for the tester to sit on.
A word of caution, you must ensure the packing material and the surface upon which it is placed is structurally capable of taking the compressive reaction load which is equal to the test load applied to the padeye.