Kerbal Space Program

I recommend enlarged versions of the R-11 Baguette and R-4 Dumpling to fit 1.25m diameter. An appropriate size for the 1.25m Baguette-derivative would have the same length of the FL-T400 tank, and the R-4 derivative would have the same length as the FL-T200.

Attached are two concepts that are along the lines of what I had in mind, along with a size comparison showing the R-11/R-4 fitting into the same length/diameter dimensions of the FL-T series tanks.