The cylinder is the part that is going to give first on an overload and then the top strap .45 blackhawk convertable cylinder is said to have 80% of the strength of a blackhwak in 44 mag , The working pressure of the the 44 mag is 40K cup this would make the .45 working pressure 32K . If you look at the loads in most manuals for 45 ruger and TC only section you will find that in fact the loads are limited to 32K .
From what I have seen the .45 super has a max pressure of 29K , So it would be fine ?.
Clarks custom guns offers the 460 rowland conversion for the blackhawk it has the same operating pressure as the 45 win mag of 40k and they must think that the 460 rowland is safe ?
I saw recently a 45 win mag cylinder for a blackhawk on Ebay and was tempted to bid but passed , I was not to sure about how safe it was.
The less pressure that is used to get the velocity the less recoil .
I have a .45 convertable and shoot acp rounds once in a while but I shoot mostly warm colt loads or bust out the FA in 454 when I want to really pop
You have to decide what is safe in your guns !!!!