Your model does look very nice. And accurate within certain tolerances. The O.D. of that 1/4" copper pipe I mentioned is about 5/16", so a 3/8" dowel is easily close enough, especially as an anchor/fitting for the hose, which goes unseen. As for the tube forward of the fittings, here's my measurement of the 1:1 print of that picture, above:
[ATTACH=full]215482[/ATTACH]
Both tubes are dead-on 1/4" O.D. So that's what I used there. Too many people don't get that tubing is measured by outer diameter and pipe (and pipe fittings) is measured by nominal inner diameter. When the two are mixed, as in something like this, it can get confusing.
1/4" tubing for the tubes running through and along the housing. Back of that is more fudge-able. Everything on your model is accurate, proportion-wise. Certainly better than my first-pass found parts. The post of mine you mentioned from ages ago, used these, found at my local Ace Hardware:
[ATTACH=full]215487[/ATTACH]
Here are those pieces, rough assembled, next to the 1:1 photo:
[ATTACH=full]215489[/ATTACH]
Whatever manufacturing differences and varying tolerances between brass and steel, I stand by the pipe measurements of those fittings as 1/8" (for the coupler and nipple) and 1/4" (for the flare nut). They are definitely not the next size up. I thought about just using the brass fittings, as this was a custom Mando and didn't need to be 100% accurate to the original, but I wanted options, and have steel fittings now, too. I need to get pictures of those to post here, as they're even closer to the originals.
As for your model... If it looks right in place, that's all anyone can ask for. Print out that picture I posted in my last post and tweak the settings until you've got it at full scale (one inch between the centers of the two closer laser hotspots, and six between the two end ones) and check your model against the originals. If you're off at all, it's by the merest fractions, and your model should be easily scalable if you feel the need to nudge it down a skosh. I'm curious what one of those, printed in polished steel from Shapeways, would look like... 
