Thanks for the encouraging comments, I do have some more ideas for additional parts, like science bits that would look a bit more interesting. I'll try to update the OP soon to make it a bit clearer and answer some questions there. The T-shaped girder is a bit tricky because on one hand, it's too short compared to stock but on the other if I make it longer it doesn't fitnwith the other adapter girders. As for the TP-250, I purposefully designed it so that the attachment node is deep enough so that 1.25 diameter parts fit tightly as well as 0.625 parts.