What suction cup did your team use? We used an Anver VC25
http://www.anver.com/document/vacuum...s-vc253545.htm
We bought a suction cup to test and our initial results were not too stellar, although this was with only students testing (no mentor oversight). We connected a suction cup to the end of a pneumatic cylinder and pulled the piston, creating decent suction on a flat surface, but poor suction on the tube. (Originally, the design called for a second cylinder,pulling the piston of the first, but we were not able to complete it with the materials we had.)
We were not dead set on a suction cup; it was one of two possible attachments to our arm, the other being a simple tong mechanism. But I would like to see if the idea can be scrapped in any kind of way.