Welcome!

Poly tunnel... Nice! I like it... Height is going to be an issue for sure though. To work around this issue, you should find a way to either SCROG or grow side ways.... I'd recommend an indica dominant strain because of height constraints. Strains that are labeled for outdoor growing are strains that are very robust and will outgrow an indoor enclosure at a rapid rate. You can pretty much choose the strain of your choice for outdoors but since this will be your first grow, I think an indica would suit you better than a fast growing/stretching sativa.... Or you can get an autflower strain.... The question you need to ask yourself is - Do I want something that is going to give me a body high or head high????

Hope this helps....

Lots of people here to answer questions but you will also have to do a lot of research yourself as well. Enjoy the ride!!!

CGI::::::