I'm not quite sure i understand what you are saying. In fact, none of this makes any sense to me. I mean, I understand how you are milling but I am not sure what happens after that. Are you leaving the milled support bar in place just reducing its mass? Is that what you are saying? IMO - once milled the bridge should be completely removed of support bars and the like, then fit to the model, adjustments made and then properly sprued. Sure, you can mills sprues on a single unit and leave them attached but when it comes to a multi element bridge it would be insane to think that there are not forces in that wax that need to be released. On another topic, casting with bars is absolutely pointless. Casting without a button is also pointless. Both are also quick ways to have issues. When metal cools it creates a vacuum and it has to pull metal from somewhere otherwise it is going to create tensions as well as porosity. Runner bars, reservoir sprues, indirect sprues, direct sprues, hollow sprues, square sprues, plastic bars, and on and on and on. It is all a complete and total waste of time. (Also a way to get more $$ out of your pocket) The only thing you need to properly sprue everything from a single anterior unit to a foll roundhouse is some rolls of spool/sprue wax and some utility wax. That is it. This is just my $0.02 worth.