Tell us more about the lay of your woods. If you are on a good slope, with 3/16 you may not need any mechanical vacuum. If you are too flat, the 3/16 will work with mechanical vacuum but may not be your best choice. Give us more details.
Put a guzzler on a small gas engine and change out to a larger gas tank, that may be your cheapest operating cost.
I run an Alamo 30 off a 5.5 hp Honda. I removed the original gas tank and I built a gas tank cradle on which I put one on that is 4.5 gal. The supplier I've bought them from a few times does not show it at this time. I got then from Surplus Center for $24.99 and free shipping. Try Ebay or amazon. Any good fuel tank that holds 4 or more gallons will be good.
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.