Converting CB Watt/SWR meter to 40m

I have a ASTATIC 10/100w meter that was orginally designed for the 11m band. I have a better one for CB now, and would like to use this one to test 40m QRP amps and transceivers. Super accurate isn't important, I just need to be able to prove that I am making positive changes when I build or modify something.

I'm thinking this should be as easy as swapping a coil inside?