I sewed a 16 inch noseeum skirt onto my 2010 SL3. It has 3/4" Velcro (loops because hooks will snag the netting) on the bottom for attaching a floor. Velcro also allows the netting to separate at the door zipper. I've tried it with the stock floor, and it works well. I intend to test it without a floor soon.
I shouldn't have used 3/4" Velcro. Narrower Velcro would suffice and weigh a little less. The bugs aren't going to be trying to pry the stuff open! ;-)
I have also added five 3 ft Triptease guylines to the additional stakeout loops. This allows for more and location-adjustable ventilation when select lines are staked out 2-3 ft away.
My SL3 tarp + guylines + netting + Velcro now weighs around 32 oz, up 7 oz from 25 oz.
The stock floor now weighs 21 oz, up 3 oz from 18 oz.
Matching the different lengths of the tarp perimeter with the floor perimeter was done by incrementally gathering the netting as I sewed on the Velcro. I ended up with around 12" extra on the floor (bottom) of the netting. This worked well because it allows me enough room to carefully enter or exit without unfastening the netting at all. The extra is carefully gathered and clipped with a few binder clips to seal it up. I also treated the netting and Velcro thoroughly with permethrin in case any ticks try to squeeze through gaps.
If you want a durable floor or to be able to leave the door open with bug protection, it's probably best, and almost a wash weight-wise, to just use the Golite nest.