Maybe st within x hangianum with longer sepals?
http://www.slippertalk.com/forum/showthread.php?t=18104
http://www.slippertalk.com/forum/showthread.php?t=18104
Because rothschildianum is pure perfection.
Okay. Maybe I should be a bit more direct. Since you haven't posted a photo, how about posting your question in the "Breeding & Production" thread. That's where we "Discuss breeding trends, flasking and seedling culture".
This is the Paph. PHOTOGRAPHY sub-forum. You're question is an interesting one. It might spark an interesting discussion; but, if it's hidden in the photo section, it'll be of no use whatsoever to ST members in the future as reference material because they won't be able to find it.
Maybe if it got backcrossed on to sanderianum, the flower could be very nice with longer sepals. Why haven't we seen more backcrossing on to sanderianum such as Lisa Hasegawa (delrosi x sand) x sand?