I know how to do it and i have done it before, but i just cant get thing to go in the ground straight. I put walls and things around the object im merging, and i use multiple doors to even out the push. I made a sketchup of a map i would like to make, and it uses some goemerging with bridges, stairs, and walls. If someone would like to show me how they geomerge, or find out what im doing wrong i would really appreciate it. My GTs are TubeSockSanchez and UnMaTch3D K1D
one thing I noticed in my geomerging experiences is that if you want it perfectly straight you need to have it completely covered on all sides with supports, otherwise it will sometimes find little pocket that it will somehow squeeze into and become crooked or lop-sided.
I suggest get your geomerging done early and when you get it in a position you like, build your map from there (make changes based on where things settle) . As well save often, and if you think ones good but not perfect, save it as a new map so you can compare it to the other next to perfects.