Roper dope it..
Here's a little trick to try when one needs to hold a engine for a no turn over. Pull any plug from the head and cram a piece of nylon rope down in the hole. Probably takes 6-10'' to lock the piston from rotating over! That will hold a thousand pounds of muscle. Good luck, pull the rope out when finished,reinstall the plug. Simple and no busted knuckles!!lol.