If you have good vacuum at the end of your lines and keep leaks in check, you are getting the best you can expect with the conditions. Finishing the season and still not being able to put a shovel in more than an inch is telling the whole story. Just wait for a winter with average snow cover and you will see a huge gain, be ready for it. Under the conditions you described the bags would not have been near as good as the tubing/vacuum set up.
Try to add some vacuum gauges, I do it by using a saddle on mains and just a T on some laterals. Every main I have has a gauge at the far end, but maybe only about 5% of my 5/16 and about 10% of my 3/16 have gauges. However even that gives me a good picture of what is going on. I have sap ladders too, but plan to eliminate them this year and next. I will start using 3/16 to climb to the main instead because of the 3/16 fact that the air (gas) does not pass the sap.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.