[Sgt_Walrus]

Hi Cross
Pyros has done this successfully in his ANZAC campaign.
I have seen quite high elevations too, 60+

My bet is that you need to set the elevation first, on open terrain...and then add the building.
That's what I would try.
The map editor sometimes doesn't like to have tiles added and subtracted too much. I laid some wire once then couldn't delete it. The icon stayed but the effects disappeared!

Use the hot key for changing elevation, it's the "asterix" (shift 8). Make the sloped hexes (bordering the one you want to be the tower) back to zero, or whatever the surrounding level should be.
This is a different command from the button on the right side of the screen that you use to set hills.
This hotkey is best used just after you have created the hex.

Have a play, you'll see what I mean.
Always do elevation first then save. Keep a few different versions of your maps as they progress. That way, if you do have to start over because the map is getting glitchy...you don't have to start from scratch.

Just some suggestions. Sorry if you already knew all that info.
Good luck.
SGT