Here's a simple one: what's the best way to generate magma mist?
Above is the basic floor plan of my entrance fortifications - a classic two-sided gatehouse, with (what will be) a raised causeway for entering caravans, flanked by lots of obsidian statues for most of its length (hence, three tile row for wagons, one tile row each for decorations == 5 tiles wide.) The one-tile wide side channels will be pumped full of magma and left open to the air for added decorative flair (and to prevent climbing ambushers from getting at the caravan too easily.) Its secondary function is to generate lots of magma mist when I chuck stuff into it for the purposes of turning siege squads into great balls of fire. However I'm not sure what the best way to generate magma mist is, or how "heavy" the things I drop into it should be.
Current options include:
1. Supports built in the magma channels, linked to levers with a single floor tile built atop of them (and maybe a statue there for good measure.) Certainly effective but a major PITA to reset after a siege.
2. A causeway above combined with stockpiles/retracting bridges/The Usual Tricks to drop obsidian blocks into the magma from above. Easy to reset but I'm not sure what constitutes "heavy enough" or how far the magma mist will reach.
3. Acceleration ramps retrofitted into the guard tower that launch minecarts at ludicrous speed down the magma channels, kicking up magma mist as they skip along the surface. I know minecarts will do this if they're moving fast enough, but I wonder what I should make them out of - lighter materiel for more range, or would a lead minecart kick up a bigger splash? If these details are a generally unknown quantity I'll default to this in the interests of educational science.