The most obvious modification from the original plan was to add the back foot. Having just one cross foot on the front bothered me as I was afraid the back leg would sink in soft or muddy soil as we are usually off a hard surface when observing. I also cut the angle on the bottom of the feet to match that on the bottom of the legs. The feet were made longer than the original plan for stability. Transportation roomis not a problem as we either use a pick-up or my wife's Grand Marquis which has a trunk large enough to transport 4 dead bodies.
Another deviation was the height of the legs. The original plan calls for 34" tall legs. After sitting in a lawn chair leaning over for a while it was nice to sit back and relax so I made the legs 48" long to provide a backrest to lean against while looking up with the naked eye or just resting. It worked perfectly for all angles of viewing with our 6" Dob which has a 48" tube.
Afraid that making the legs longer would change the angles on the feet and most certainly the lenght of the brace, I assembled the two legs and the seat then put them together on the floor and used a level on the seat, spreading the legs until the seat was level. Then using an adjustable protractor I measured the angle against the floot. The original angles and layout of the seat plan worked fine. I also measured the length of the aluminum brace at this time.
The original plan calls for a piece of cardboard added to the spacer block on the bottom of the seat to provide clearance between the brackets for sliding. Instead, I cut the spacer block out of a scrap piece of 2" x 6" so I could make the block the width I needed.
Instead of using lag bolts to secure the feet to the legs, I used 5/16" T-Nuts with lock and flat washers. A clearance hole is drilled and the nuts driven in which provide a very solid attachment. I salvaged these from an old dining room table. Four T-Nuts and 5/16" bolts will be required if you make both front and rear feet and attach with this method.
The only frustrating thing about this chair is the grip of the seat on the rail. I used clear vinyl tubing for grip material on the seat bolts instead of rubber fuel line. The chair would slip on the finish and may be due to the vinyl instead of rubber tubing. I added strips of adhesive backed none slip to the front and back of the front leg and it tears and the pressure points. I think this is due to the adhesive used sliding. Using polyurethane glue to attach it may prevent this, or using rubber fuel line without the grip strip instead of the vinyl may solve this.
Finally, I changed the way the velcro attached to keep the whole thing bundled together. A wrap around the legs does not secure the seat which fell down when carried. This method secures the legs, brace and the seat in one secure package.
I will be adding handles on either side of the legs at the balance point to make carrying the chair easier.
This chair works absolutely great and the grip strip problem is a very MINOR annoyance that I will solve at some date in the future.
Please email me and let me know if you have used this site to build a chair and how it worked out for you.