I'm quite new to dealing with HVAC duct-work.
We would like to install a suspended ceiling in this room. Since the finished ceiling will be higher than this duct-work, we're going to build drywall bulkheads around them.
In order to reduce the wasted space (and having to build more bulkheads), we were thinking of running the two 7-inch ducts from the end of the main duct. This way we can build a single bulkhead around the main duct and continue it, containing the two smaller ducts, to the exterior wall where they turn apart and run upstairs. Both 7-inch lines lead to registers in the floor immediately above, approximately 10 feet apart, on the same wall.
Are there any good reasons not to do this (such as loss of pressure in one of the lines)? Would it be better to replace those two lines with a larger conduit and branch it when it reaches the wall?