Nice pics Jocko, and this is definitely an area that I find interesting, though I probably would take the lazy man's approach and use the free "Cumulus" plug-in. You can use it pre(using a cloud picture object with an alpha), or post in PS or other image editors that can use the plug. I know a clever, hard-working artist can get good smoke using Bryce, but the most convincing smoke I've seen in a Bryce still-shot still has had a "little help". The best smoke I've seen in a Bryce animation was done using a free cover -disc ver. of "ParticleIllusion SE 2.0".