i'm not sure about that mount i know other have used it, welcome to the forums, and glad to see another mad force owner here.
are you talking about the stock kyosho force .21 or the ofna force .21? if its the ofna then yes that mount will work, but kyosho also has there own mount to mount any upgrade motor to stock, but you going to need a few other things tho, here's a online web manual and a list of what you need.
http://rcdocuments.com/Kyosho%20MAD%...E%20Manual.pdf
http://rcdocuments.com/Kyosho%20MAD%...ded%20View.pdf
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Your choice of shoes and spring(s)