I seem to remember a website selling miranda/avenger interior plans, they were pretty well detailed interior plans, I think I saw em four or five years ago, Have googled around and can't seem to find em anymore....anyone still remember this site?
You're probably thinking of the Strategic Design blueprints. That company is now defunct and the only source I know is previews of the first few pages (just external views, no deckplans) on the Star Trek Bluebrint Database.
Probably thinking of Federation Frontiers: http://federationfrontiers.tripod.com/#avenger-miranda Very detailed and overall amazing.
The site you speak of is Cygnus-X1. POST EDITED TO REMOVE CONTENT NOT ALLOWED BY TREKBBS RULES - DO NOT POST METHODS TO CIRCUMVENT SECURITY MEASURES ON OTHER WEBSITES
I do know that the Star Trek Blueprint Database is at cygnus-x1.net and I do know that they still have many of the supposedly offline blueprint pages still uploaded on their servers even though none of the actual pages link to them, but I didn't wanna mention that last part because I'm not quite sure about the legality of it. Anyway, OP seems to have found what he was looking for, so I guess it's a moot point now.
So long as everyone's clear that none of the unauthorized editions are "official" in the eyes of CBS/Paramount - until/unless they say otherwise - everyone seems to be okay with it. This sort of unofficial stuff's been making the rounds for at least three decades, since before the Internet. I remember ads in the classifieds pages of Starlog... That said, announcing these links was just plain rude. (Also, I'm still planning on buying hardcopy editions from the designers.)
You're quite welcome. I can only imagine how much work those things were. Now GO DO MORE!!! (Wasn't there a refit E set hinted at?)