The new (CVS) version as of 9/10/06 always creates all positive-only gerber files. This should
increase the number of fabs that are happy with pcb's gerber files.
There are 5 styles of thermals available, all of which are formed entirely from
holes (or lack thereof for solid thermals) cut in the polygon. Thus there are no
thermal "fingers" which can bump into or cause clearance violations with other
structures. The command-line interface to changing the thermal (on the current
layer) is ":SetThermal(Object|Selected|SelectedPins|SelectedVias, x)"
where x is the thermal style, a number 0 through 5.... read more