Did you see the post on giant gesneriads over at Hort Log? We don't get to see photos of things like Paraboea all that much. The post also includes a photo of a Rhytidophyllum tomentosum at a botanic garden in Europe. Do any of the U.S. botanical gardens have larger gesneriads on public display? I saw a young R. tomentosum at the Tsukuba Botanical Garden a couple of hours outside of Tokyo:
Anyway, if you haven't seen it already, check out the Hort Log post.