I've tried everything whats the trick to stopping the oil leak at the oil filter support arm where it attaches to the engine block.

Sorry, I can't really help you, but I can say what I know. If it ain't leakin', it ain't British.

Have you replaced the seal?

Replace the seal and use a little gasket maker around the edges. If you can afford it buy one of the remote filter kits. Much easier to change the oil. Leaking British cars are a sign of careless work.

Look for hairline cracks in the mounting base

Raymond.

If you are cranking the bolts down REALLY hard, you are killing the gasket... Are you using a good gasket sealer?? I use permatex aircraft sealer.. (comes in a little jar.. stuff is nasty brown) follow the instructions and use a new gasket.. If it's not cracked then this stuff should fix it.. I have never had a leak yet..

For this same problem, how much should you torque the square filter and oil filter adapter down?
Thanks, Jazzydo