how much weight can i tow?

Bedlam wrote:
If you have an overhang off the rear of the TC, you will get interference between the tongue and bottom of the TC when going through dips or curbed driveways.

I thought so too but in thousands of miles and years of doing it, it hasn't been a problem. It helps if you have a 4x4 truck that sits a little higher, and the camper elevated a little off the truck bed floor.
Conversely, under the same dip/curbed driveway situation with a hitch extension you can bottom out on the ground.

I know it's custom work and not a premade bolt-on solution but it's not a difficult modification and a welding shop can do it for you if you haven't got a sawzall and a wire-feed. If you stretch your trailer tongue I recommend adding a couple square-tube or angle-iron crossmembers to prevent the C-channel from twisting, and add some triangular gussets in every corner you can.

I think if any trailer tongue were to fail it would be at the rear of the tongue just ahead of the trailer, so add a lot of "beef" there in particular.

I added a flat panel on top of my trailer tongue so it became a step for the camper.

The only drawback I've encountered has been that I had to remove my tongue jack to clear under the camper. One of these days I'll get around to simply relocating it further back but until then I just use a floor jack.