Here are some quotes from the topics on Big Gemini over at M6:
"If this going to be a modern varient you want to put a shuttle style docking adapter at the rear instead of the apollo type.
What you want to do to make this is use the same capsule but make three new pieces. The Capsule extension, the new retro section, the adapter with docking cone. With the new beta coming out we can have the camera swing to the rear to represent the rear crew station." -estar (Robert Conley)
"I don't want this to be a modernized Big Gemini (for now)I believe this add on should simulate the Big Gemini how it was originally intended to be used, maybe someone can even do an MOL for it to fly to. Then later someone could come up with modern variants."
-gladiator1332 (Mike Majeski)
"So basically how the modeling will go...The crew module will be the normal Gemini B capsule, followed by the passenger compartment which will have to be modeled (I could most-likely use parts of the Gemini B capsule to make this part) The retro module will just be the normal retro module from the Gemini add on, just larger. The cargo module will just be a sized up maneuvering module. The pressurized tunnel will be the attachment point for the cargo and passenger compartment. This way when you jettison the cargo module, the tunnel doesnt go with it. Only until you jettison the retro module do you lose the presurized tunnel. Then after all that we just have the docking adapter." -gladiator1332 (Mike Majeski)