John,
I set aside a couple of hours yesterday and finally built the signal buffer kit. Haven't had time to test it over the entire layout but in preliminary testing 3 locomotives responded well on different segments of the layout. I plan to add the pot and resistor modification and noticed the component layout is different on the kit PCB than the production unit PCB shown in the online picture of the modification. Is R5 the correct resistor to replace in the kit version PCB? Thanks for your help and all of your contribution to the Forum and to the hobby.