We had our 7 and 8 on trolleys for quite some time.
There are several designs out there but if you get stuck, drop me an email address and I will send you a snap of a sketch. It is for our 12 building table, but is adaptable. 3" and 4" x 2" CLS lumber, a good blockboard top and carpet tiles for protection. Its an afternoon's easy work after sketching to suit.
The main thing is access - you need to be able to bend into the fuselage easily. We are building a 14 as well and will keep the forward fuselage low on a trolley for some time. Yep, trial fit the undercarriage but once it is on it is high and access into the fuselage becomes a pain.
The fuselage needs to rest across the spar area. If you have the rear fuselage on, consider making two separate tables or trolleys, they can be customised to the correct height. If you put the tables on casters make sure they will take the load and that all of them have brakes
Also consider the weight and balance - you will have to ballast the tail and strap it down.
Home Despot or Lowes do good casters.
The 8 table was around 2' high - that low !
You can do lots of good work on the engine and canopy while it is down there and accessible. Also, if you arrange the set up to have the side rails absolutely level, fitting the wings can also be done if you have space in the shop - all the measurements are easier.