IMHO and limited experience...
I had the same concerns with my RR Merlin V-12 model, but when the engine was complete except for lack of starter I got impatient and decided to try hand prop'ing it anyway (did put on leather gloves thou) and to my great surprise it was easy to start by hand.
in contrast to a single cylinder engine which needs to be going at a high RPM to get started because there's not much momentum in the prop and crankshaft (no flywheel), on a multi cylinder engine there's always a cylinder that's firing, at least if there are enough cylinders. With the geared Merlin V-12 a cylinder fires every 30-degrees of prop rotation, so if you push it by hand through 1/3 of a revolution you're pushing through 4 firings, any one of which will get the engine going on its own.
I'm guessing the 5 cylinder radial is going to be maybe tricky to hand start, its not geared, so the engine only fires every 144-degrees, so you can only hand push it through a single firing at a time. (a 9 cylinder fires every 80-deg, so you'll get 2 firings per hand push which should be almost as easy as the V-12)
would like to know what your experience is if/when you try it.