You could make it so the slabs line back up for anyone using the mod, and by the slabs I mean the ones that are like 3 pixels off, or you could also make it so it shows what percentage you are into the level above the slider at the top that make scrolls through the level.
Please stick to one suggestion at a time - this is why the template is set up the way it is.
Resizing the 'slab'-type blocks to be exactly half a block in size is outside the scope of BetterEdit for exactly the reason you mentioned - it would only work for people with the mod.
The level percentage thing is a good suggestion and was present in 2.1, but may be difficult (though not impossible?) in 2.2 due to gameplay rotations. Please make a new issue for this and use the template appropriately.
You could make it so the slabs line back up for anyone using the mod, and by the slabs I mean the ones that are like 3 pixels off, or you could also make it so it shows what percentage you are into the level above the slider at the top that make scrolls through the level.