The biggest problem with switching to LiFeP04 batteries is the amount of work involved, operating in small spaces.
I highly recommend developing a detailed plan before ever starting this project. That plan should not only be a drawing and parts list, it should be detailed as to the order of the steps and exact placement for installation of each and every component. For instance, the last component that I installed was the automatic transfer switch. I didn't know they existed. Had I developed a plan, I would have installed that component 1st because of it's size and where I decided to install it. Space being a premium in the rear storage locker, I decided to install the transfer switch in the void between the shower wall and the bathtub (next to the WFCO converter). That meant that I had to remove the Progressive Dynamics converter and the WFCO control panel (that I had just spent hours installing) to gain access to my intended area. I also had to cut a 10"x 10" hole in the wall (shown in the pic above, covered by a vent grate).
I failed to do that because I didn't take the complexity of the change seriously. That lead to a bunch of redoes, wasted $ on parts that weren't adequate for the job and a lot of labor hours. With a proper plan, I could have (easily) completed this entire install in a weekend. As it was, this install took me nearly 3 weeks. Partially because it's summer and I needed lots of breaks but mostly due to waiting for parts to arrive as I discovered that a certain wire size was wrong (order, wait 2-days). Then I discovered that a certain fuse wasn't right and I needed a special circuit breaker (order, wait 2-days). I needed a special tool, (order, wait 2-days). On and on it went.
All I can say is, "over size" most everything. What you pay in a few extra $, will likely save you in redoes, aggravation and wasted $ in wrong parts. This isn't just a matter of installing a new battery.........
. These LiFeP04 batteries can put out thousands of amps and the wiring in the TM is simply not adequate for the job. If something shorts out with one of these batteries, there is a likelihood of a fire.