Chuck,
If you're referring to the tongue extension with the red Silverado pickup truck in the pics that I posted, that particular set up belongs to my friend Wayne. He trailers his Seaward 22 to the club each year with it. Actually, he built that tongue extension for his trailer and it works great. I think that the tongue is 10' long and is the same dimension as his trailer tongue which is probably 3 1/2" square stock tube. He's using galvanized steel plates for the bracket. I really don't have any of the dimensions for any of that. I've been able to launch my boat without a tongue extension because my trailer is long enough to get her into deep water. So I'm pretty lucky in that respect. I've seen some pretty simple extension rigs though. One of the guys who used to be in my club had a home made trailer that he rigged for his 24' cabin cruiser. The tongue that he made up was separate from the trailer and it didn't even have a coupler on it. He was pretty good at welding and cutting with a torch, and what he did was to cut a large key hole near the end of the tongue for the ball to fit in. The the round hole was big enough for the ball to fit into, and slide forward into the short narrow slot to lock it in. It was shaped like a skeleton key slot. He had a hole in the side of the tongue for a bolt to lock it in. All he did was place the tongue in a bracket that he welded to his trailer, on one side of the trailer tongue and bolted it in. It worked OK at the ramp and he was able to get his boat on or off his trailer. I wish that I had taken some pics of it. I never see him much, as he left the club a few years ago and bought a smaller boat with a trailer. I know that Wayne has a coupler on his tongue and he uses a pin to lock the tongue in place. Both Wayne, and this other guy named Leo are pretty clever when it comes to "Mickey Mousing." I've stolen a lot of ideas of Wayne. Sometimes I irk Wayne by improving on his ideas, but if it wasn't for him, I wouldn't have been able to come up with those ideas myself in the first place. I wish that I could be of more help to you Chuck. So, good luck with that.
Joe