people running really thick oils, like 30w70, i hope you like sludgy motors, cause thats what its gonna cause.
also, excessively thick oil increases oil pressure in your big ends and mains, this elevated pressure can have a hugeee effect on surface temperatures of the bearings, and in my book i would avoid that, and run the thinner oil, 20w50 is still thick.
i don't even run oil that thick in my 15 year old 300K diesel, not a big fan of penrite as they try to push thicker than recommended oils, which cause sludging, i use shell in my diesel, and at the moment my 3t has the old oil out of my diesel in it, but for a motor i care about i would be looking at shell or castrol, theres alot of info on oils if you care to read it all, all the codes that say it complies with this and that, if you read them you will find alot of things interesting, the reason i use shell in mine is cause it meets a certain aus standard, but not other international ones cause it has such a high content of some really good lubricating stuff, banned overseas cause its not the best for the environment...
twinky, are you saying the oil drains out of the head while the motors running, or after shutdown?