The back wall gets a 2x4 that is 60" long aprox
No ledger board on the ends though.
You may need to shim the apron depending on how level your floor is. All wood framed buildings are designed to carry the weight of a tub.
I want to install a CI kohler villager (unless not recommended) in my 20+yo townhouse on the 2nd floor. Do I have to put extra support on the beams under the subfloor? Also, how long should the 2x4 for the back wall ledger be? Will a 2x4 fit for a ledger on the wall opposite of the drain?
A 2x4 may be too "thick" for the apron on the villager tub, UNLESS you bevel the edge so it will not hit the curve on the tub. I use a 1x4.
Licensed residential and commercial plumber