In my '76 FLH, I replaced the OEM hydraulics with Velva-Touch, back in the early 80's. Vern Ott recommended 20W-50 for proper operation, so I moved from 60W synthetic to 20W-50 (both Amsoil). It had 20W-50 with every oil change right up until I totaled the bike in '04. The bike was my primary cross-country ride, with 78K miles on it when it came off the road.
My '59 FLH has always been my 'at home' bike, and I ran the same 20W-50 synthetic in it. However, I had solid adapters in it, rather than hydraulics. It finally died on my last August ('08; purchased it and put it on the road in the Fall of '74) and I have just recently put it back on the road, with 10W-40 Amsoil as break-in oil, along with OEM hydraulics back in place of the solids. Bike runs good on the short runs that I'm making for the time being. But, when the oil warms up, the lifters/valves become very noisy. I have switched to 20W-50, as the ambient temps here in North Central N.Carolina have become much warmer, so I need the bit heavier viscosity for the OEM hydraulics to pump up properly. Later on, I'll switch to 60W Amsoil, when I put it out on the road for some serious distance travels.
My point is: 60W is a must for the OEM hydraulics to perform properly, when the engine and oil are hot. Other than that, I've proven that 20W-50 gives excellent protection in both Shovels and Pans.
Jack
P.S. - I love AMF technology. I've also proven that it would take me anywhere in the U.S. that I wanted to go. The '76 has been in every state, but R.I., Hawaii, and Alaska.