Trekker4747 has provided a concise summary of the issue. To illustrate it, I would refer to this interview with Andrew Probert:
http://www.trekplace.com/ap2005int01.html
Check out the interview starting with question # 23. Another issue is, of course, the angle of the large windows in the crew's quarters (way too steep).
And there's still the question where to locate the observation lounge on the
Enterprise-D from the opening shot in "Encounter at Farpoint" (the conference lounge is at the back of the bridge).
I already wonder how they are going to do this in the "special edition" of TNG one day, when they will use an uninterrupted CGI camera zoom onto Picard (but considering how amazingly they did this in the TOS-R opening shot in "The Cage" I'm confident it's gonna look great).
I think the size of the windows of the
Enterprise-D is a visual hint of technical evolution in the 24th Century compared to the state-of-the-art in the 23rd Century. Some windows of the
Enterprise-A already then were rather large (e.g. main recreation room starboard aft).
Unfortunately, we didn't see that many exterior windows in TOS, except for Captain Pike's quarters in TOS-R (probably somewhere below the bridge), the hangar deck and in "The Mark of Gideon".
In my humble opinion they could have CGI inserted one or two windows in one of the many TOS conference rooms (to suggest some are at the outer saucer rim), but that's a different story.
Bob