Cara,
SWD is a nightmare. After tending very productive raspberries for a few years, I must say the last 2 were bad. I did get 1/2 seasons worth of blackberries from my Arapahoes in '13, but after a couple weeks they were infested. I have Blueberries but am concentrating on the earliest/latest varieties cause they aren't as active at those temps. No more brambles for me.

Mosquito or no-see-um type mesh is plenty small, will work to bag individual clusters. Not familiar with tulle. Eggs could still be laid where the berry firmly contacts the netting.

I would not recommend fully netting the whole patch because many of the overwintering flies may be on the ground in the patch. You would just end up with a tent full of flies.

Set out a vinegar trap so you know when the flies start to appear.

it will be very interesting to see how swd overwinters this year in the northern ,locations. lots of hard cold without much snow cover.
The recs i have seen are for netting to go up as green berries swell, well before any color or skin softening.
you have to have the netting off for pollinators.

For many varieties, the terminal berry at the apex of each cluster turns color while other berries are still green, so the netting should be up by then.

Thanks for the feedback. I wonder if there's someway I can make 'hoops' in the bag to try and keep the netting around the fruit but not touching it. I'm going to give it a try this year and hope for the best.

I would be so happy if the SWD took a hard hit this winter. Freeze little bastards.