To overcome the problem with using the multi-page layout issue, you might be able to get a large piece of poster paper (large enough for your full image and then some), then, only cutting off the edges which would overlap another tile, tape the first printed inkjet piece down to the cardboard using the remaining margin edges. For the next piece, only cut off the edges which overlap, and tape it down (using remaining edges), do the next the same and so on, until you have them all laying there flat, aligned "perfectly", taped down to the poster paper. If you try to go 3x3 tile wise or larger, the inner pieces will need to retian their sides, and outer pieces will overlap the "dead zone".
Another quick trick - instead of trying to print & cut to exact edges, have the art on your tiles overlap enough to offset any sloppy printing, you can still line up the image without having to be the worlds best scissor handler.
Anyway, then you would lay the side panel onto the image (this part will remain tricky and in need of a skilled eye, I wouldn't try it will a full cab, but a cabaret side and smaller I would), and finally tape the whole poster paper contraption to the wood from the underside (use a few boards like mini-saw horses to elevate the poster paper and slip some tape under) so it's very firmly in place, then carefully flip the whole thing and do your image rub down.
Thickness of poster paper "support" layer will impact how easy/well you can rub the image, and the thickness of what you're printing on will determine how well overlapping works.
One final thought, you can also print on to transparency paper so you can see the image from both sides, and then you can try aligning from "the top". Again, having the art on the tiles overlap will help avoid gaps/misalignment.