I am looking to do this mod over the weekend in preparation for towing my sailboat XC. I too went with the BM 70264 only to discover the inlet/outlet fittings are 5/16. I already purchased extra 3/8 hose and it sloppy loose on the cooler fittings. I know some have purchased a reducer fitting, but for others, has simply tightening the hose clamp over the "flexible" hose worked? From my limited research it seems like the return line PSI is not terribly high, but the consequences of a hose coming off is potentially catastrophic for the tranny. I'm not too keen on introducing more connections from a reducing barb fitting, but I also want to do it right. The alternative is going 5/16 and stretching it over the 10mm hard lines, but that's not ideal either. F, B&M, advertise your damn dimensions properly... Anyone want to help me solve this incredibly difficult first world problem?