You might need to do a little modifying to get that type of chair to work without a headache rack, but it can be done.....you'll just have to have more anchor points going to the corners of the pickup bed to help secure the rig. Mine attaches to both the headache rack and another support bar attaches to the bed-rail near the tailgate. I would thing that you could have more of these supports to make it sturdy.
Here's a shot of mine, with all the credit going to Randy Watson for his great ideas and overall help.
Here are some of the measurements of my rig. I went ahead and built a headache rack for my truck because this will make the whole set-up rock solid, but I'm sure you can come up with a hybrid from the other ideas that the guys on this board have come up with to build theirs.
Here's a pic of the base of the rig...
Here's some measurements of the actual shooting chair & rest....keep in mind that it is setting upside down.
Here is the saddles that are mounted on the inside of the 3" X 3" angle iron bed rails which hold the bottom cross piece of the whole set-up....(this picture is actually from Randy Watson's set-up)
And here's a rear view of how it sets in the back of the truck....
You can see the piece of square tubing angling down from the area around the footrest down to the back corner of the bed. I would think that you would need more of these (and use heavier material) to help stabilize your seat if you weren't wanting to anchor it to a headache rack.
Feel free to contact me with any questions.
BTW....there is no "light man" needed since the spotlight is mounted to the front of the shooting rest. It's a hands-free system that works great!
Hope this helps!
God Bless you and yours!
Rusty