My Coral Honeysuckle has an enormous trunk and I assume root system but my Gold Flame is still relatively small by comparison maybe only 2 inches in diameter at the most but it was very small when I got it in 2010. I had a Dropmore Scarlet for a couple of years but the last year the aphids really worked it over good and it never returned the next year.
I am not quite sure what you mean by planting them together. Were you wanting to plant them in the same hole? If that is the case I don't think so. If you were putting them on an arbor and planting one on each side of the arbor that would work. My coral is about 6 yrs. old now and I an using three 8 ft trellises side by side for that one. I just ordered a Major Wheeler and I will probably keep it in a large container for the time being until I get a spot picked out for it.
USDA hardiness zone 6a
Heat zone 4
Sunset zone 39