If you're using
radar, then I think that's a perfectly reasonable solution (I sailed a big Swan that was set up like that, and it was nice).
I think you might find 7" to be a wee bit cramped for
charts, however. Can you swing for 8" (or 8.5" or whatever the next size is)?
The new MFD's are higher resolution than the older ones were, so if you have the right reading glasses on (!) you can get more information out of a given
screen size than used to be the case. I have replaced a 10.5" display with an 8" display at my nav table and I am happy -- the old display was VGA (640 * 480) and the new one is SVGA (800 x 600) despite the smaller screen. 8" is pretty good, although pushing it a bit if you want to split the screen to see
radar and chart at the same time.
The new MFD's show so much different information that having two of them is a good idea, IMHO. I could't physically fit two either at my
helm or at the nav table, or I would definitely have gone with one 8" and one 7" at each position. The 7" MFD's are dirt
cheap, like a
wind instrument used to cost. Under $1000 in the U.S.