My Traveller needs a new crossmember and floors.

I have seen suggestions that that best way to install the crossmember is to cut it in two pieces -- 1/3 and 2/3.
I presume the idea is that the floor on one side and 2/3 of the crossmember, then replace the other floor and 1/3 crossmember.
I presume the idea of this approach is that this would make the job easier to handle and reduce the chance of the body gaining a permanent twist.
Does all this this sound right?
Does anyone have other suggestions?
Cheers
Don