Having emailed with Rick about it a bit, the impression I got was that the perspective drawing* was simply a more final version of the design, so I'm content to make that the target. In fact, when I showed him our design with the flat sides, that was his only feedback: make it the planar sides more blended like the TNG tricorder.
Also, if you look even at the straght-on view closely, you'll see that the curvature is gently suggested with a single tiny line
As far as my own interest in this project and my own build: my desire is not really to use these sketches as an excuse to spawn an infinite variety of new non-canon tricorder designs, but simply to make the actual tricorder-that-would-have-been for Voyager. As far as other versions, though, I'm happy to give you technical help in developing those, either with laser cutting styrene or 3D modeling, depending on how you feel once you've seen the aforementioned styrene pieces I'm sending.
I am considering this an exercise in make-believe product development, since planning out how the actual physical build will be assembled and how the electronics will interface with it is surprisingly analogous to that professional concern.. It turns out to be surprisingly complicated and even just designing this thing virtually first with the aid of CAD software; it gives me so much respect for folks like @stapleton13 building something like the Mark VII using his "cowboy" scratch-build methods. I can't help but wonder how many iterations he had to go through to sort out stuff like how the doors mate together to ensure that the hinge works and the door stays open at just the right angle. Make one small change throws everything else off, as I've learned somewhat painfully in working on this project from design to design.
*I've been calling it "isometric," but I took measurements yesterday and it's not. =\