There's a map for UFO even smaller than the Small Scout! Only it doesn't appear in the game.
No idea what its use was supposed to be, but it goes from "horribly cramped" to "painfully-to-look cramped". It's one thing to shoot them with incendiary munition, and another to stuff them in folding undercarriage and leave there. Ahem.
How to use
To use the map UFO1B in OpenXCom you'll need renamed copies of Small Scout entries in "ufos:" and "alienDeployments:" sections and a custom single-tile data set. The former have to be modified like this:
name: UFO1B mapDataSets: - BLANK1 - UFO1 - BLANKS mapBlocks: - name: UFO1B width: 2 length: 2
Tile indices have correct relative positions, but are misplaced by 1, and would be drawn incorrectly. To fix this you'll also need a single-tile data set in TERRAIN. I called it BLANK1.MCD, because it's a copy of the first half (62 bytes) of BLANKS.MCD, while BLANK1.PCK and BLANK1.TAB can be simple copies of respective BLANKS files.
This may cause some obscure bugs, but unlikely - the host terrain already has BLANKS for both normal uses.
If you know a way to automatically replace tile indices, that would be better, but this works. Unfortunately, it's not so easy with UFO_000 and UFO_010: they apparently use relative positions of the tiles different from release MCDs (as one can see using Bomb Bloke's numerical tileset) thus the only way to reanimate those maps is actual replacement - or remake.
Landing legs are the same as in UFO1A, only stand in 2x2 square.