Hey Ruger62. I have the B-Square 9-13" which I like. It comes with a screw in extension which extends to 21" for sitting position. I need a 23" for knealing position. The B-Square, and Harris come with a universal adaptor which will fit a forstock sling stud. Both have an adaptor for the mini which fits on the gas block. I installed a sling swivel stud on my Hogue stock so I didn't need an adaptor.
If you haven't found it yet click on the search button, enter bipods, click on "any date", select mini-14 forum. Many post will come up on that subject.