Strangely, our laser-cut terrain wasn't quite sitting perfectly over a printed playing surface of 1" squares. Over an 8 inch board section, the actual laser-cut walls were about 2mm over-sized.
It was no big deal - simply placing the walls just 1mm off their printed map, all the way around, gave the illusion of them fitting properly.
But knowing that they were ever-so-slightly oversized was grating.
A quick look on the intertubes revealed that some other LS3020 owners had experienced similar issues. The DPI of the laser is set to 1016 as it leaves the HPC factory, but after multiple cut-and-measure processes, we discovered that 1003 (horizontal) and 1004 (vertical) give exact sizes for both large and small shapes
(it's easy to miss that small shapes are over-/under-sized because 1% of a 5mm shape is tiny. But on larger shapes, even a 1% difference in expected and actual sizes can become noticeable).
With the laser cutter configured properly, we tried cutting out our amended wall shapes. This time the walls are a bit lower (but the door frames remain their original size).
The new wall sections fitted together reassuringly closely. Where we've been cutting a 3mm slot ever-so-slightly oversized, we're now cutting it dead on - which means that, thanks to the kerf (the slightly angled cut edge of the material) where two pieces slot into each other, the fit is very snug indeed.
At times - and particularly when slotting pieces into thin sections where doorframes are placed - this can cause the mdf to twist a little; especially since we tried to use superglue on the joints to save time. This means there's no time for adjustments once the joint has been made - which in turn means that on occasion we ended up gluing a section with a slight twist in it. This can be ironed out on the next version; it's hardly noticeable (but, like being slightly oversized, we know it's there!)
The finished map looked similar to the earlier one, only this time the smaller rooms look much more accessible, even for tiny 15mm models.
The walls still look "inkeeping" with the 15mm/20mm scale; it's clear to see which sections are separated from which, even through the wall is lower.
Even with the lower walls, long, thin corridors keep their slightly "claustrophobic" feeling, while still allowing the player to pick up the miniatures from even the smallest and tightest of rooms.
In short, we much prefer this design to the earlier one.
Now we just need to get some stickers made up to disguise the nasty burnt-edge appearance of the mdf, to make it look like the interior of a spaceship, or some sci-fi themed moon base or something!