Hi Hans
This is the dream arrangement in my mind, to have a wider field scope collecting the RGB and a longer FL scope collecting the Lum/Ha would be great. LRGB style imaging is very time consuming so being able to effectively halve the total time spent would be a god send..especially when tackling say 140hrs
It's a no brainer really and combining the results from two systems is quite straight forward. It basically comes down to having the two scopes and two cameras in the first place and shooting the Luminance through the system that provides the best image scale and the RGB through the other, the RGB can be quite low resolution and still deliver superb final LRGB results
Depending on the two scopes you plan to tandem you may need to consider a beefier mount if you don't already have one though...or two separate mounts
Mike