QSL Teutonic Saddle question

I just picked up a "Teutonic QSL 1000 Mile Solo Saddle" to try out on my 1972 R75 /5, but I have a question about mounting this thing to my bike.
I have the seat, spring and base plate (the piece that slides into the frame top tube and has a horizontal rod sticking across the back making a "T") all assembled and slid into the frametop tube. The question is "What holds the seat at the rear?
A friend told me to use hose clamps to hold it on to the frame's cross tube but that doesn't seem real strong. From just looking at it, I would guess that there might be some sort of bracket or clamp that I am missing.
If there are any folks out there who could help with this puzzle, please let me know.
Oh yeah, the /5 looks really sharp with this seat, original black touring tank and the black Wixom bags with white pinstripes!

Thats about right. Basically U have to modify it as U see fit. I've looked at quite a few in the past and I've seen it done several ways and most mounts look abit amateurish at best. They do look neat on the bike. U will probably lose the use of your under the seat tool box. I have seen the tool box retained, with some of the sidewalls cleared a way for the seat mount to to get acess to the oval frame tube. Good luck with your project.

The seat did come with a curved bar that went below the cross bar and attached to the main mount. I found the bar to be such a PIA to remove/re-install when I worked on my /5 that I left it off. Just sitting on the saddle kept it in place, tho' I admit I didn't do any off-roading. If I still had the /5, I'd probably be using zip ties to hold the bracket down.

BTW - It the springs are a little weak, put a tennis ball between the seat and the bracket - worked for me.

Thanks for the replies, Barry & Chris. I have designed a brace that will mount under the base plate and over the cross tube and will behaving it made up at a local machine shop. I still wish that I could see the "curved bar" that Chris mentioned just to see if I am re-inventing the wheel or if I'm improving it!
I think that I will try that tennis ball idea; I'm around 200 lbs and the saddle does drop a bit when I'm on it!
Thanks again guys!