I've got my plug ready. Got my resin, glass and picked up some graphite powder for surface coat. 

I have also found the vacuum storage bag not to be ideal, it does hold but not real good, so it's not a nice vacuum.  I have some aluminum tape so I may attempt to cut one in half and seal it with tape, possibly making a better seal.

If you want to cut the coasts you can always use thick garbage bag, and seal it with some bathroom silicone and zip ties.   but this way sucks. Invest 30 £ more and get proper vacuum stuff. Trust me you can ruin your part if for ex. Your bag will not be stretchy enough it could be torn apart by the vacuum. You don't have to use perforated film or breather cloth, cheap peel ply and toilet paper will do the job. I would never replace bagging film and bagging tape with some cheap s***, all your work depends on that. if you are creative you can make your bag reusable as you prepare special seal for that ,that's how I do with most of my bags.