My Hasler hatch has a sliding closing piece built into it, and closing it is the work of a moment - and yet I've never ever felt that closing it quickly would have contributed to my safety or comfort. I think it extremely unlikely that you'll see the really bad sea coming, the one that's going to roll you, in time to do anything about it.
As Bob says, in all "normal" bad weather, up to and including a moderate knockdown, the pramhood copes well. The hurricane cover is only going to be fitted as a last resort, when you've decided that you can do nothing more on deck, streamed the drogue and retired to your berth.
I would only use the system shown in PJR fig 13.17 and I can't see that the pramhood needs to be rotated to any particular position to be able to hinge the cover into place. The pramhood needs to be lowered, that's all. I'd fit a webbing strap such that you can hold the pramhood down flat, where it won't take any harm.
Galway Blazer was very light and narrow for her length, and thus very susceptible to knockdown and rollover. La Chica is the opposite, with a hullform that is reckoned the best by C A Marchaj for resisting such things. I would think her very unlikely to be rolled through 360, and that's the only time you're going to get hundreds of gallons below.
In Tystie's only severe knockdown, to an angle that caused everything in the cockpit to go into the water, only about 3 gallons came below through the open pramhood hatch. The pramhood itself got slightly damaged, through the force of the water hitting it, which is why I say to strap it down when the cover is in place.
PS Put a clear window in the pramhood, so that you can see to windward without lowering it.