Always use the clutch Chris,, with the anti reverse engaged .I just cannot get on with backwinding at all, the clutch if fettled correctly is as smooth as any other modern reels clutch, it does exactly what it is supposed to do if correctly set. I have never ever lost a fish because the clutch did not work correctly, its all about servicing your reels and making sure they work as designed to.
Well I have three 301's, one 411 and one Match, all bought new. These reels I used wholesale from my first 301 which I bought in 1971/2. I never trusted the clutches I'm sad to say, they were never reliably smooth, always a little stuttery. Thus I became an expert at back winding.
I bought my first Shimano, a 3000 GTM, about 25 years ago, and I must say, the drag system was a revelation, especially with the fighting drag.
Luckily I invested in two more of these, one of which is a Stradic before the prices for the Japanese models went through the roof.
I admire your skill using the 300's, well done that man. I may still drag one of my 301's out of the cupboard... After all, all my Mitchells were serviced by Mitchell down in Southampton before they were mothballed.