Ah. In that regard, something to be aware of - DOS Lemmings (and by extension, Lemmix) require all steel area coordinates and sizes to be multiples of 4. Additionally, to minimize steel-digging glitches, steel areas generally should extend slightly beyond the edge of the steel pieces. In NeoLemmix on the other hand, steel area coordinates/sizes can be pixel-perfect, and this is generally expected, because of the difference in how steel is handled. Specifically, in DOS, a lemming can destroy a steel pixel, but will generally stop performing the destructive skill upon encountering it (and in the case of a bomber, it's all-or-nothing - if they're standing on steel, no damage is done, if they're not, everything within their radius, even steel, is destroyed). On the other hand, in NeoLemmix, steel pixels are actually indestructible.
Anyway, I'll have a go at this sometime and let you know my feedback. It might take a while, since I don't have as much spare time as I sometimes do at the moment (it sorta comes and goes as to when I do or don't), so the time I do have for Lemmings is generally being spent on completing my playthrough of Lemmings Reunion (great pack, I'd highly recommend playing it if you haven't already) and working on the NeoLemmix Introduction Pack.