I spliced in some 6" plastic pipe parts into my system. It worked great except on really cold days, when it can crack if you accidentally pick up a rock.
Haven't tried that, but I did use 6" galvanized duct/smoke pipe when I was testing my system with an old hose that was just a little too short. Worked pretty well, then i plunked down the $ for some good flex tubing from McMaster-carr that has served me well.
Yankeerider, can you give me a little more detail on the tubing from McMaster-carr? Went to their web site and found quite a selection of flexible tubing?
I needed new 6" tubing for my Trac-Vac. I found the local Chamberlin rubber store had a much better quality hose at a very reasonable price. and they cut it to whatever length you need. I think I bought 8 or 10 feet of it.
Raykos-
The stuff I am using is on page 208 of their current online catalog. It's called "Economical Rubber Duct Hose" made of EPDM rubber. The 6" size is 7.87/ft . There's also a version with a wear strip which I didn't get. This is probably the fifth year of use I've gotten out of it, and so far no obvious deterioration.