... good representation of FB-109, BS-110A and BS-113A sections, the dimension you want is 4.1/8" (4.125"), as shown below. Another handy trick is to print a duplicate template on tracing paper (use an ink-jet printer, one sheet at a time). You can then lay this on the rail tops during construction, to check and confirm the alignments. (If expense is no object, you can print on OHP transparency sheets.) regards, Martin. outer_fb_rail_foot.png posted: 10 Jun 2009 20:11 from: MikeTrice Thanks for this. I am guessing the vast majority of users are more interested in bullhead rail, which kind of keeps flatbottom support shunted down the priority list. I hadn't appreciated the issues relating to the rail being canted at 1 in 20 as I don't tend to try and recreate it in model form, so full marks for trying to get it right. Another option, which others might like to comment on, is the possibility of doing an interim release ...