Hi,
I have just purchased a set of EM Concrete Sleepers Bases and Code 83 FB rail from the store. The rail is a very very tight fit in the track bases.
PECO code 82 would probably be a better fit but is is no longer made and the C&L and PECO code 83 is well undersize.
I persevered with the EMGS code 83 and EM Concrete Sleeper Base. You simply need to modify the rail. It only needs 0.01mm taken off the base width and you can do that by running the rail through some wet and dry. Then the rail slides in far easier.
The rail has the right inclination (1:20) in the base and is exactly 18.2mm between the inside of the rail heads measured at the top.
Patrick