I wouldn't recommend planting it to grow through C. armandii, that plant grows rampantly throughout the summer and will crowd out the Betty Corning. You could use a 6 foot obelisk - height and spread for Betty Corning in 200mm x 50mm, so you'd find the growth would droop back down over the support. And yes, it would be too crowded to grow an earlier flowering variety on the same obelisk - the earlier one is likely to produce a lot of leaf growth during summer, and the Betty Corning may get buried under it.

Otherwise, its quite good for growing up large roses or shrubs which don't need frequent trimming in summer and autumn and which also don't put on rampant growth (rhododendron for instance). This one needs cutting down annually to about 8-10 inches in midwinter, or by mid February at the latest.

I planted one about 2 years ago against a fence with clematis mesh - I have to say, it appears to prefer going sideways to the Escallonia planted next to it and scrambling up that... bit of a pain, because the Escallonia is kept well trimmed throughout summer.

Thanks very much Bamboo. I do have some large roses--maigold, complicata and A Shropshire Lad. I like that idea--now to decide which would be best! Thanks for the pruning advice too. I'm glad it can be cut back so hard and not become overwhelming!

Not only can it be cut back, it must be, otherwise, the following summer (if its not done in winter) you end up with lots of dead looking brown stems 8 feet long with new growth all at the top...

Ooer! Mustn't forget then!
Thank you.