You can download the Garmin mounting templates and make a test on the electronics dshboard, thats what i usually do in such cases; to cut a sheet of cardboard to size and bring it to the boat to make sure the shape fit.
I saw several Bimini/Canyon what have similar/same size electronics panel and they had twin 8412 and the autopilot and yamaha gauge between them. That looked clean and nice but only 12", from what is saw on the 330 Express i guess that they will not fit without modifications on the panel.
Even if the 8416 would fit, consder that you need enough space around them to screw the 8416 down on the panel and basically you would have to cut the whole front of the instrumen panel to make them fit, leaving only a small strip between them for stability.
I personally see no particular benefit of 16" mfd's, 12" is just fine as distance from seat to the mfd's is not very far.
Chris