You need to make sure it's contrasting enough. Have you looked at the Lutoslawski Dance Preludes or the Poulenc sonata? The Lutoslawski is about 10 minutes (so you'd need some vicious cuts in the tutti passages of the Stamitz); the second and third movements of the Poulenc come in at about 9 minutes.
As for the conclusion, play around with the running order and find out what works best, and be prepared to be asked about the running order in the Viva.
If it helps, my programme comprised the Finzi

(hint: learn all the technical terms for fugues and a few other Finzi works

), the outer movements of the Saint-Saens and the final two movements of the Weber Grand Duo Concertant. Reverse chronological order, starting and finishing with a bang, return of the first movement of the Saint-Saens at the end of the last made for an aesthetically pleasing arch structure...