Re: Hive top feeder issues
Bees will build comb in areas wider than beespace(max 3/8 inch) in what they consider their hive.
IMHO, I think a way to avoid the bridge comb is to get the feeder above an inner cover with some vertical space between the feeder and inner cover. Idea is that they will go for syrup but not use space above inner cover as part of hive.
I have a vent box, built out of 2x4 material that is a "mini super", if you will. I have two 1 inch screened holes on each side. Vent box is installed immediately above the inner cover. Have a super above that with frames of candied honey that the bees are slowly cleaning up and moving to honey super below the inner cover.
Am not familiar with the Dadant feeder but built the Millar feeder on the Build It Yourself section of home page. It has a 3/4 inch vertical wood slot that bees enter from the bottom. It is not an inverted V as is the Mann Lake one. I added a 3/8 rim to bottom. Forget whether I used an inner cover when I used it, but had minimal bridge comb.
Zone 3b. If you always do what you always did, you'll always get what you always got!