So I feel kind of stupid for asking this but if you don't know ask right?
Regarding the addition of neck reinforcements I have a 1936 Dobro M32 that simply is unplayable (action at the 12th fret is measuring out at nearly 1/4") due to the neck needing to be reset as well as the permanent relief. With this instrument I am not concerned with the vintage value, I really only care about it's musical value at this point.
Compression fretting did exactly jack squat for the previous owner (he might not have had done it correctly but that's beside the point) so I'd like to add some stability to the neck and straighten it.
What I would like to do is simply add a cf rod (only 1) down the middle of the neck to give it some resistance against the pull of the strings. It has nothing as you can see from the photo below (and yes the removal should've been cleaner, that's my fault)
My question is, after the channel is routed for the carbon reinforcement, is it necessary to add a shim to the top of the cf rod under the fingerboard or is it safe to simply have the cf rod flush with the top of the neck and make direct contact with the fingerboard?