What a difference collection above the blade makes, eh? I popped for a Shark Guard and added a 4"/2 1/2" splitter so I now have both above the blade and below the blade removal as well. The over arm method you're using makes a lot of sense and is a really good option to keep cost moderate. I have an over-arm type collector sitting in a box that one of these days I'll likely sell.
Any collection device must stop the swarf that comes over the top of the blade. Not always so easy since it's coming out at close to 100 mph. Not much time for the air flow to catch them. The Shark guard stops these with an angled lucite block that reaches almost to the table or workpiece. Even then, a little bit of sawdust still gets away. Can you drop your collector down to just above the table or workpiece, or is the height fixed?
The more I do, the less I accomplish.