I pull a Burley Encore with a road bike. I use the chainstay mount, but I think the skewer hitch would be better on a modern road bike.

I have three road bikes - two 1980's steel bikes and a 2000 Cannondale R800. The R800 has short, fat aluminum chainstays and I can hit the hitch mount with my heel if I'm not careful, but it's not a major problem. I never hit the hitch on either of the steel bikes.

I mostly ride on a local paved trail, but I do ride a mile or so on the road from my house to the local trail. There is one large hill on this route and it's located so I have to climb it on my way home.

The Cannondale is a 39X53 double crank and that gearing is fine for me.

One of the 80's steel bikes is a Centurion with a 42-tooth small ring and a smallish 7-speed cassette. It's a bit tough to crank up the hill going home at the end of the ride, and I find myself in the bottom two or three gears if there's much of a headwind, but it works okay.

The other steel bike is a Schwinn Passage. It's set up as a 42x18 fixed gear. That means 20+ mph at 90 rpm... a little tall for the flat and requires some serious strength for the hills. I can power up the big hill on the way home without a whole lot of trouble, but I wouldn't want to pull a trailer with a 70+ gear-inch fixed gear over very many hills.

The chainstay mount will mar your finish, so I recommend getting a skewer-mount. My bikes are older, and I'm not that anal, so it's okay for me.

"Strength" of the frame will not be an issue. You aren't going to be putting more force onto the frame unless you get stronger legs.

Gearing is acceptable with my double-equipped road bikes, FOR ME. You may be weaker or may like to ride hillier terrain. Unfortunately, I live in a city and I don't feel comfortable pulling the trailer on the local roads.