[TowerTalk] phased vertical feedline question

[WW3S]

Planning on phasing (christman method) 2 verticals for 40m, one a Butternut 
HF6 and the other either another HF6 or a 40m vertical. I'd like to be able 
to use the HF6 as a multiband antenna for a second radio. It uses a matching 
stub of RG-11 on 20m. How complex would it be to continue to use that stub 
so the antenna could continue to be used on 20m, and still be part of an 
array on 40?