Maple folks I need your opinions!

First: I have formed the two vees where the sap will set in the WRU from 18 guage stainless. Yes its a little heavy but the price was right. I can get 18 guage stainless tubing for the steam pipes thru the sap at a very reasonable cost per foot compared to copper. I know copper is a much better heat conductor but I am strongly considering going with the 2 inch stainless steam pipes. I will try to post a picture. Comments are welcome.

Second: Also I will be able to have about 20 gallons of sap heating in the WRU at any one time does this sound about right for a 3 x 10? Sap will be about 6.5 to 7 inches deep. With out rebuilding the Vees this is what I will go with.

Third: Suggestion was made to me that a blower for a hot tub might work very well for the air supply for the bubbler in the WRU? I was sketching up a manifold system of 1/2 inch dia copper air pipes that would be feed through 1 inch copper. Rather that a air box in the end of the WRU. Again comments will be entertained.

Fourth and last: I would like to run the sap in one end of the Vee on the left side at the back, bring the sap to the front of that Vee transfer it through a tube to the front of the right Vee and then exit at the back of the right Vee.
Seems to me this would allow the sap to dwell longer and have a longer path to drive off more steam. The Vees would operate in Series rather than parallel. I know most of the ones that I have seen are not made this way. Can anyone describe the pros and cons of this approach?

Regards,
Chris