i think i have to agree with festus. if it was working for you before cdub then it was probably a bug back then and it has now been fixed. i also have never heard of anyone doing what it is your trying there. support is for exterior overhangs and infill is for interior. you can always crank down the infill % until its really low. it just needs to be enough to bridge over. 7-10% and a couple extra top layers should still give you a nice surface and less mass than using support.