I'd email Redline's tech support and see what they say. The "Vtwin" aspect of it is news to me too as I run the std shockproof and MTL.. Probably just another way of making more money though. Their Vtwin 20W50 is also a lot more than their std 20W50.. Probably just a little more of a certain ingrediant in an oil and they are greedy..
On a side note, I use 10W30 Amsoil in my Honda outboard and they came out with a marine version of the 10W30. I emailed Amsoil, and he said to continue using the regular 10W30 as it was cheaper. At least he was honest.
I haven't followed much of the oil propaganda in the past few years, but if the standard 20W50 oil you refer to is for automotive use, it's designed for watercooled motors and the temp its designed to working within is a lot different than an air cooled motor. There could be a 60 to 80 degree difference in operating temps between water cooled and air cooled motors, especially our V-Twin bikes.
I would also think that the "V-Twin" rating is primarily directed to Harleys and or "other" air cooled V-twin bikes. I doubt they could say "Harley" oil on their containers.
Just be sure that you're using cooling specific oil for your application.
Just my 2 cents of rambling information.
Hey, one question.... I've read this thread and I have to plead ingnorance on the subject, what is MTL? I know you're all using it in the primary, but what does MTL stand for?
Now I'm done.
Thanks.