Mine is a 7'x14' tandem ,for me its the perfect size. Two Touring bikes staggered with some extra space for odds and ends. Have a small remote camera install in the trailer and a monitor in cab of truck so I can keep a eye on things as I'm going down the road.
Thistle

 

I have a 7X16. I can carry two bikes staggered and extra stuff. It works just fine. If you go 7X16 make sure it has the wheels to the outside of the trailer (not cut into the inside)

However, when I bought this trailer, they had an 8X16 sitting right beside it. I decided that the hassle of towing a trailer 1 foot wider wasn't worth it. If I did it again, I would opt for the extra foot. I don't carry bikes often, but that extra foot would be nice.

 

I don't have an enclosed trailer, but I would recommend staggering the bikes if you want to hauls two baggers. It gives you a lot more room. Just buy a trailer 2 feet longer than you were going to.

This holds two Street Glides no problem and it's a 6 1/2' x 12' Dove tail.
I'm sure an enclosed trailer would need to be wider. Just to make it easier to strap the bikes down.

 

IMHO a V-nose is the way to go. I have pulled many trailers through the years snowmobile racing. A V-nose does make a difference pulling, at least a couple mpg compared to a flat front. The newer inline trailers (7 footers) are great to pull.

I haven't trailered my bike yet. Do most of you guys just strap them down or use the front wheel chock and straps?

 

You have 2 ways to go. You can either get a shorter, 8' wide trailer like say an 8 x 10 or get a slightly longer 7'-er (ie.7 x 12). The advantage with the wider unit is being able to haul 2 EG's side by side. With a narrower trailer you have to stagger them. Also, I've never found one design to deliver better fuel mileage over another and I've owned several. You will see a mileage difference if you can afford an aluminum trailer that actually weighs less than the same steel model - not all of them do.

 

I have one of these:
http://www.homesteadertrailer.com/as...r_hercules.asp

I have the 8x10. It fits my Ultra and a roadking staggered. I really like it a lot, best
trailer I have owned, pulls easy as well, bought it as a leftover and bargained down even further due to the economy.