Arg. I’m having limited fun with Dual extrusion ABS and HIPS at present. Almost all of these problems are slicing software related it seems.
I’ve been using Cura of late as my machine is so similar to an Ultimaker, but it’s support capability is a bit immature and it has some annoying gaps in it’s features, like setting a different nozzle size and flow rate for each extruder and any control over thresholds for where you get support structures.
I kind of hate slic3r and I’ve not used it in ages - It took 5 minutes to slice something that cura did in 45 seconds when I gave it a go this evening and produced some really strange gcode.
So, this leaves me with kisslicer… I like kisslicer, once you get over the crazy UI and settings layout, it is the most controllable and feature rich slicer but dual extruder capability comes at a cost of 42USD which I wouldn’t complain about normally but there is some ambiguity as to whether Kiss will continue to be developed.
So, anyone with dual extrusion HIPS experience have suggestions?
I love KISSlicer for doing fully-supported prints. I’ve been pretty happy with the results.But, as you have pointed out, its future seems a bit iffy.
The best HIPS+ABS print I saw of a sphere on a support bed was the result of MakerWare. In theory, you should be able to massage the gcode output from MakerWare (MiracleGrue) to work with a Marlin-based printer.
My vote is slic3r for dual head printers. Two heads is definitely harder than one! I’m about to try 3 and I’m hesitant 
4 sounds ridiculous.
@Tim_Rastall try the latest version of slic3r. they’ve re-written a lot of the engine in C++ and made some really good speed & mem improvements. also 3d preview!
@Brook_Drumm I’ve been having some success with twin heads; the nozzle heights are just right etc, I just need more control over where supports are created and how the fist few layers of support are deposited. I know slic3r will do this but after using kiss and Cura it’s hard to go back to slic3r. Having some control over steps/mm for each extruder in marlin would also be nice, I was surprised when I discovered it didn’t do that.