The axle location is determined by the door location, and also by tongue weight.
And there are benefits of having the axle further back. It's easier to tow, and you won't have the kind of sway problems that the bigger rv's with the more centered axles have. Believe me, you don't want a sway problem. I saw an RV get destroyed on the highway right in front of me because he couldn't control his sway!
Now, how is axle location determined? One guy came up with a formula that starts with the axle 34.5" from the rear, and moves forward 6" for every 1' in length. That's actually a pretty good starting poing, except that if you have a heavy teardrop, your tongue is really heavy.
You can tweak your axle location with the spreadsheets that Rik and Andrew have... they are stored on Andrews web site, and are really easy to use.
http://www.angib.pwp.blueyonder.co.uk/t ... tear45.htm
As an example, my Weekender is going to be 117" long or 9' 9". Based on the formula my axle should be 45" from the rear of the teardrop. Using the spreadsheet, I decide to put it 49" from the rear of the teardrop, to take some weight off the tongue so I can tow it with the Jetta. I still have 68" from the front of the teardrop to the axle, so sway should not be an issue.
As it so happens I took a photo of exactly that yesterday... Here ya go... hope it helps!!!
Mike...
The quality is remembered long after the price is forgotten, so build your teardrop with the best materials...