It's fascinating to me how these proportions have flummoxed many a modeller and have led to a debate over which is a more accurate representation of the craft over all.
I have seen a number of modellers attempt some major modifications of their kits and I don't know whether it was wise looking at their final products. The only modification I wanted to make (and did) was with the engines. I was never a fan of the straight up blue/white engines from the film - especially when George re-did the scene where the Falcon takes off from Mos Eisley and you get to see that gorgeous detailing of its rear engines. Shapeways coming out with their engine inserts was a master stroke for those of us looking to add a little more interest to the rear of the Shuttle.
As it stands, I love the aesthetic of the MPC kit - despite its flaws - and I'm looking forward to realising my preferred iteration of the kit.
As I write this, I'm waiting on some cabling so I can complete the electronics, then I'll be glueing the two halves of the main hull together. It's a task I'm rather nervous about but I purchased a set of clamps that I think will do the task I need.