One suggestion is to try making masks out of thin brass shim stock, available at many hardware or modeling stores, before going with 3-D printing. You should be able to find some that is just thin enough to lie flat and can then use the negatives to align the pieces. Overlapping metal seems to work fine in all of the four-blade easels I've used and taping them on the upper surface would allow you to reposition them until you get the composition right.