That scope has a ~50mm diameter objective body (not lens), with a 30mm tube. So there's about 10mm of objective hanging below the tube bottom, or 0.4", which is usually just a little too high for a medium, so you'd need a high ring if you were mounting on a model where the mount/rail is under the entire scope (like a Ruger Precision Rifle, or AR-15). BUT!!!! Since you're not mounting on a flat top rail, and your Seekins base isn't full length, you'll be able to lower the scope, so medium will work fine, maybe even lows.
One trick - since you have the rifle and the optic - grab an old deck of playing cards and cut the whole deck into quarters, lock the rifle in a vise, set the decks of card strips on the optic rail and set the scope on it, with the adjustment boss between the stacks of cards. Take cards out of both stacks until your objective bell is about 1/8" clear of the barrel. Measure the thickness of the stack, that's the ring height you need.