I confess I just bunch up the plastic because I'm notoriously bad at building anything. Your idea sounds way better.
Just a word of caution...a single layer of plastic in zone 5 probably won't get you through midwinter.

I roll ends around PVC pipe and secure with extra landscape pavers. I secure plastic to hoops.

I agree that there's no way you'll go thru winter with just one layer of plastic if you want to pick greens over the winter. I tried that last year (along with 2 cold frames), and I needed two layers, plus two sets of doubled row cover. And I get tremendous sun and used water inside for heat retention. If you're simply overwintering, you'll need row cover under plastic. Johnny's has videos and equipment.

Dan

dan

not sure where along the front range you're located but i'm also here. i live in fort collins. i wasn't interested in doing double layers with air between, etc., but may have to reconsider if we want fresh greens all winter, which was my original objective. regardless it sounds like adjustment of expectations is in order.

I use bricks, but you have to lay them down neatly one after another, or the wind will get in. On the sides, too, I use six bricks per side, all told, some 22 bricks per bed.
I have a lot of bricks.

Perhaps it is colder there than here, but here it is certainly not sunny in winter. Collard and kale make it under a single layer, and collard can be picked frozen. It is not efficient, a lot of outer leaves die and become inedible, but it is much better than nothing.

The best thermal ballast is moist, uncovered soil. No mulch whatsoever. I usually water (with a 5-gallons bucket) when I open a bed, and I am meticoulous when I close it. I leave the snow on, because I just overwinter whole beds, and that helps. I suggest you experiment with one bed, single layer, just red kale, and see how it goes. If red kale dies, it is proof positive that you have to go double.

Glib is right about the mulch, particularly organic mulches. When I was starting out with protected culture, I foolishly mulched and I was actually getting *colder* temperatures inside on mulched soil, than outside on bare soil.

Dude, you can PM me, I'm in Aurora. In this (newish) location, I'm prepping for my 4th year all winter.

Dan

In a slightly milder climate, I can use one layer of plastic (well, so far...who knows now from year to year?) but I cut it very long, then I fold it over the ends and use the PVC clips to hold it on. Very tight seal and it keeps wind out. Some of the plastic I have I did not cut long enough, but I can bump it up by adding old shower curtains to an end.

I stapled one end this spring (plus one side was stapled (it was on a raised bed), but I wouldn't do that again. It was cheap Menards plastic, so I'm not out much. I put weights on the other end after bunching it up (after tightening everything up).

thanks dan. will send you a pm before long.