You might be overthinking this. I've used both seperately in the past but lately I just go with the floating row cover of varying thicknesses. When I want a more protection I would just double-up on the row cover. Last year when I harvested my final pepper crop I had 4 layers of Agribon-30 on the remaining 100' section of rows and the final rollup and storage was simplified.
I can't say that I use low tunnels anymore. In the spring I just stick wire hoops at intervals to protect delicate crops but for most crops Ag-19 won't hurt crops if applied directly over them. When I first saw floating row covers used in 1994 by a supply firm/grower it was amazing that lopes were almost full size under unsupported fabric in mid April. The fabric was just balooning over the crop in the light breeze.

Thankyou for responding! We are at 4000' with fairly cool summers compared to some. My warm weather crops have been really hit or miss; ie Okra, Peppers, etc. I currently only have one 24x75 high tunnel and it is designated to tomatoes in the warm months.

It was in the Nolts catalog that I saw the perforated row cover. It claims to create a "green house" like environment so it would offer the heat that I'm looking for. My thoughts on Agribon under this was for pest protection (as the perforated would allow bugs to creep thru). Did you find that the perforated plastic kept the temperature higher than the Agribon? I'd happily opt for multiple layers of Agribon but it's not cheap (though re-useable). Thankyou again for the response!

The biggest difference between the perforated plastic film and the Agribon IMO is that you get virtually no rain water penetrating the plastic. The slits will allow excess heat to escape but temps tend to rise higher under the film. I consider it more risky than Agribon with no real added benefit.
Certain farmers lay the perforated plastic over early planted sweet corn and that strategy works for the equipment they use to apply and later remove and dispose of the plastic but in your case you'll need to anchor the plastic in much the same way as the Agribon- with rocks, logs or the bags of sand (listed just before the perforated plastic in Nolts catalog). That's the main reason why I like to cover 6 rows at a time so less sand bags are needed per row. My ordering choices are the 26' or 30' Agribon width rolls. Niether Agribon or the plastic are cheap but I often get 5-8 years use out of my Agribon.