Mini hoop greenhouse

I have spent the last few months researching low cost greenhouses. Currently, one of the requirements of my vegetable garden is that it not only provides my family with a constant supply of food for the summer and for winter storage but to also allow us to reduce our family's food costs. As a result I can't justify spending 1000's or 10s of thousands of dollars on a greenhouse to raise a few thousands dollars worth of food. One of the main challenges of getting a good yield in Alberta is dealing with the very short growing season.  Therefore, if i can build an unheated greenhouse that allows me to extend the growing season by 1 month in the spring and 1 month in the fall i will be very happy.
I stumbled upon the idea of hoop greenhouses using PVC pipe and inexpensive poly.  This seems to fit all of my requirements.I am still uncertain as to whether I need to build a full size greenhouse as it might be that row covers would fulfill my purpose.I have already purchased two 6'x20' foot floating fabric row covers to use for frost protection as well as barriers for insects and other pests.Perhaps I should put up a few "portable" row covers using poly in the early spring and then change them to the fabric covers once summer hits or remove them altogether.The only vegetable that has problems with the row cover idea is the tomatoes.   Typically my plants grow to 6 feet even with extensive pruning.  I am going to need a fullsize hoop greenhouse to cover them I guess.
I am only able to have a small garden in my backyard due to the lot size and the nearly total shade that is provided by huge popular trees.  The last two years I have had access to a much larger plot across town so that is where I grow most of my vegetables.  In my backyard I have a small raised bed (~5.5' x 10').  I like to fill this with a various assortment of vegetables that I can pick from readily without having to drive across town to my large garden.  I decided to build a small hoop house over the raised bed.  Not only will this allow me to get an earlier start on spring, I can also use it as a cold frame for all the hardier plants I have started indoors including some bedding plant such as geraniums, pansies, violas, marigolds.  I currently have 10 4' flourscents indoors scattered around my house and I have just about run out of space to stuff all the plants as I transplant them into larger containers.
I figure this small hoop will be a prototype for a large hoop house if I decide to build it.  I started by pounding 3' lengths of rebar into the four corners of the raised bed and then 3 more along the length at appoximately 30" spacings.My rasied bed is probably much deeper then I really need so 3' rebar was just enough.  In harder ground 2.5' would probably be good enough.I then used 10' lengths of white 1/2 inch PVC pipe to use as hoops. I had bought some metal strapping to use to fasten the pipe to the sides of the rasied bed but after putting up the pipe I figured I didn't really need it. If this were a larger house I would definietly use it though.

 The widest plastic I could find was 102" and I needed to find a way to join two pieces.  I decided to overlap two pieces by about 6' which would give a length of about 15.5" and a width of 12'.  I wasn't really sure what the best way to join the pieces together would be.  For a larger house I would definetly research this some more and try to get a single piece of poly. I just used some clear packing tape on the top and bottom sides of the overlapping join.  I think this will hold ok.  We will see how well it holds up after a few rains. I think the two hardest parts of making a hoop house are putting the poly up with wind and making sure not to puncture the poly. I ended up using some 1x6 boards as strapping to hold the plastic in place allong the sides.
This used material I had on hand as i am cheap, so I am not exactly sure what I would use if I didn't have this. I personally don't know if I like the idea of just using staples.It seems like they would just rip in a wind storm.
I also tried cutting a 3" piece of black 1/2" poly pipe that had been slit along the length.  I thought these could be used as a clamp.I tried putting them on quickly but found that the rough corners where I cut ended up punctering the poly as I put it on.This might be a good solution if the edges were filed smooth but it seems like it would still rub and puncture eventually.
I still don't know the best/easiest way to finish the ends.  I have some overlapping poly that I have currently just wrapped around and held down by extra planks.I think I need to build two walls on the ends with some type of door.The other thing I haven't figured out is how to make one of the sides roll up a couple of feet in the summer to allow access for harvesting/weeding/watering.I think this design might not support this unless I cut vertical slits near the ends to make a flap or something.
You can see my current progress in the pictures below.