Hi Ian,
I can vouch for what BrisGreg said about the flat trolley.
My mate and I use one to move our 10" Dob around and it's great.
It's stable enough to leave the scope on it while we use it.
There's also an excellent article here for moving your Dob. around safely.
http://www.iceinspace.com.au/63-12-0-0-1-0.html
Ken.