I've had the RC-20XL for a while now, and now I'm thinking of how I can get more out of it.
First of all, I want to add an external tap tempo that can be synced with my DD-20's tap tempo. I'd imagine that all it would take would be to wire a jack to the tap tempo button in the RC-20XL and use a switch with a Y connector that splits the signal to both pedals, but I'd like a more experienced opinion.
I'd also like to know why the pedal has a minimum recording time, and if this can be changed.
It depends on how the switches are wired as I know some of Boss stuff uses normally closed switches while others us normally closed. You will have to do some investigating with a DMM. Also to be safe I would use a DP switch and keep the signals split as I doubt the two units will like sharing the same logic input.
As for the recording time I would say that is a software thing one of the developers needed to do and many loopers have that limit. You cannot change it as it is in the software.
Andrew