If you're only going to build one TD/TTT, then go for it !
It's just a few additional curves here and there. While camping,
just level it fore and aft with one side slightly higher than the
other for any roof water drainage, otherwise I see no practical
objections that would recommend to not build it.
The hatch could be dealt with by making one with a straight
line side bottom that would overlap the TD body sides to close. The hatch
sides would then be used to continue to define the 'cloud body's'
top shape, and then use horizontal spars spanning from them for the
roof support. [See this example:
http://tnttt.com/viewtopic.php?p=984642#p984642You could do the rear slanted side body line straight, not the same as
the rear cloud top side outline of the hatch, for the straight line
hatch side bottoms to seal against.] A couple layers of thin
plywood [1/8 inch over here, your metric counterpart over there.]
could be used to sheath the spars and provide the roof structure
surface to place your exterior roof cover on. If AL, just do any
seams at/on the top of the curves, well sealed, obviously.
Place the hatch hinge at the topmost part/location on whichever
cloud roof curve section you deem appropriate.
Member Designs is the area most post such designs in.
http://tnttt.com/viewforum.php?f=27If you develop it further, maybe park it there, or in your
build thread if you go ahead with it. And put a link to each
"other thread" in the respective threads you have going now
that would pertain to it.
If you have a house - you have a hobby.