Band saws can be a bit more tricky to collect. Depends on the machine, and how many ports it has.
Machines with 1 port, particularly smaller machines, are very inefficient because they are just collecting what the wheel drags into the lower case. 2 port machines are much better because they are also collecting directly below the lower guide bearings. This is where most collection on bandsaws falls short. There are various ways to fashion a custom made port that fastens under the table.
But I have to ask what exactly do you mean by "still a lot of dust not being collected?"
If its accumulating inside the machine don't worry about it. No matter how good your collection, dust will still accumulate in corners.
My point is if you're not getting the desired collection with a bandsaw, its very likely an issue with the machine, not the collector.