Got weird problem with proftweak

[curious aardvark]

So I'm seriously trying to get dual extrusion working.
Given up on simplify3d - doesn't actually print a purge wall just a single line scrape and that doesn't print until the second layer. By which time it's much too late to save the print.

So figured I'd go back to makerware and use proftweak to slow the first layer down - it's either that or print the whole thing at 10 mm/s - which might end up being my only option.

Everytime I try and run proftweak - either from makerware or direct from the .json file, I just get a file called: 'javaw.exe' opening up in notepad.

I have uninstalled and reinstalled proftweak a couple times. I've even set proftweak to be the default program for .json files. Nothing makes any difference.

Currently have notepad set as default editor for profiles and that does seem to work.

So what the hell has happened to proftweak ?
Anyone got a clue.

[curious aardvark]

Okay so I've managed to print a decent dual extrusion print. Wahey !

Now just need to know which of the many weird settings in the makerbot profile controls the overlap between two different materials during a dual print.

I need to increase it - but can't find anything called 'overlap'. except 'spur overlap'
Could that be it ?

"doExternalSpurs": true,
"doInternalSpurs": false,
"maxSpurWidth": 0.5,
"minSpurLength": 0.4,
"minSpurWidth": 0.12,
"spurOverlap": 0.001,

Apparently not.

Okay I'll just try and 'squidge' the edges together lol