920T will no doubt be stronger than the 715C. If your 715C is OOB, then it should be 2000 polished. With the 920T having more surface because it is at 4000 will be able to handle more oil. Also if you feel that it doesn't, you can always take the surface down some more. I have another 920T coming, that I will put a pin up drilling like my 715C, but put my surface at 2000 to see how much more it will read the midlane.
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