is there any reason why a guy couldnt buy some tarp and design his own shelter? I havent seen the subject mentioned, although I may have missed it.
I was thinking of basically an 8x5 foot leanto with precut sides and front. Grommets would be added to secure it. Seems like it would be alot cheaper than someone elses idea of a tent and would be designed by the person who would need it.
It would be erected in Wisconsin so trees would be plentiful for support.
Am I missing something?

In Lowes or HD in the tool section there will be a small display or product made by "General Tools" and they make a grommet tool http://www.generaltools.com/directory.asp?action=ppage&pnum=58&sectionid=4
You could use small pvc pipe since it will bend to make hoops if needed. I was thinking of making large hoops that fit on the bed of my truck like a covered wagon and making up a tarp to cover it.

No reason at all. Just remember to use good thread when you do any stitching.

Along with nylon canvas and the like, you might want to look at Tyvek. You can buy it in rolls that are something like eight or nine feet wide, and it will pack a lot smaller and lighter than any kind of canvas. But it probably won't take the beating. It's also plain, glossy white, so it will stick out like a sore thumb so long as it isn't in snow.

try looking at
http://www.backpacking.net/makegear.html
they may give you an idea or two

Designing and producing your own tarp seems like a good idea to me. I'd thought I would like to do that as well, but the lack of a sewing machine or the skills to use one has me looking into other options.

If I could find a seamstress that worked for less than I've used in the past, to sew some of my nuttier creations together, I'd think about going that route as well.

Grommets are the easy part.

If you haven't done so already, check out the Tarp Shelter Introduction here at ETS.

Just remember that inspite of Bucky Fuller and his plethora of ugly mushroom domes somebody has tried just about every concievable tent design allready. Look through the many tent companies online, read the classics by Rustrum and then invest in some cheap sheeting and good old duct tape. A temporary mockup can reveal ( literal) shortcomings that can leave your feet outside for porcupines to chew on.

Excellent idea!
As far as sewing goes, I had planned to simply use closely spaced (6 inches?) grommets and use paracord to hold it together. That way I could use the tarp sides or attach precut netting sides and use the tarp sides for other thngs.

This is from the ETS website and you may find it very useful. I did. Tarp shelters.

Have a look at the Tarp Tents. Lots of user feedback can be had here.