NOTE: edited loss figure error in bold below.
Not sure about the "KMR", but 25 feet of LMR400 would only have about 0.092 0.675 dB loss.
I use and suggest the 'flex' version of whatever coax brand you like. I use TM LMR400 UltraFlex for almost everything. I realize it's expensive, but compared to the rest of the radio/antenna investment, it's not a big portion.
We just talked about the difference between regular and flex type coax in another thread and the advantages of flex is that it is easier to work with (your advantage), can be bent into a tighter radius and can be more easily repurposed if you change setups.
The LMR240/240UF is decent coax, but at GMRS frequencies, I think it will have more loss than you want (@450mHz - 5.3dB/100 feet for LMR240 vs 2.7dB/100 for LMR400). It IS physically much easier to work with and much lighter than the 400 series, but you'd still probably want to used the 'flex' version in either case.
Specs:
https://timesmicrowave.com/cables/lmr-240-uf-coax-cables/
https://timesmicrowave.com/cables/lmr-400-uf-coax-cables/
Loss tables:
https://www.w4rp.com/ref/coax.html