I'll echo Paul, and suggest mocking it up and not only looking at it, but touching the controls and pretending to make changes to the 430, as you might in flight. My thought being you'll then get a feel for the compromises you're making between scan height on the 430, and the ergonomics of stack.
Concur that the 240 and 327 will be touched least often, so having them higher, almost out of the way, and having the 430 closer to your throttle hand may be something you like...that is if the scan of the 430 screen remains comfortable to your eyes. How important that might be may depend on whether you have another moving map in the panel (EFIS, 696, etc) for SA, or if the 430 is your only moving map.
Mission requirements will also help define what you like. Lots of IFR and no other moving map, that screen placement may be top pri. Mostly VFR and lots of formation, small distances from throttle to the frequency change knob may be a feature you'll like.
You might do it in the current arrangement, and then again in another arrangement that puts the screen where you want it but might require rib surgery, to see what works best visually and ergonomically.
Caveat, I don't have a 430, but in my -6 I have a 396 on top of a 340/SL-40/327 stack, and I spend a lot of time playing with the 396 on X-Cs (scrolling, paging, checking wx, etc). Its my only moving map, so high is good for scan and sunlight readability, and I rest my fingers on the glareshield and mash buttons with my thumb to rest my forearm sometimes (actually often). From that experience, I think I'd want a 430 either low or high for manipulating the controls, and high if it was my only map.
Just some thoughts...chair flying it is really a good way to get a feel for what works for you.
Cheers,
Bob