You are aware that the CB&Q didn't purchase, nor run, FT A-B-A units? The CB&Q FT models had the A & B units connected together by draw bars, thus they only operated them as A+B - B+A until the purchased F2A units. Then the FT four unit sets were "broken up" into FTA+FTB-F2A consists. Those Sunset/3rd Rail models are really nice though.
Hot water I know that. Until I can install kadees on the FTB unit ( They came with drawbars on the A units). My only option is to run ABA or AA. I plan on running AB due to the length of my sidings on my current Layout. New one in the planning stages will allow ABA in the sidings in the yard.. Also, CBQ had used F2s with the FTA/Bs but I have found some pics with an F3 similar what GN had done. I plan on posting pics and questions in my other thread. The big thing is Kadee mounts( Spacers)
Doug