Do you think using bags reduces the hop flavor and aroma? I used bags before, but felt like my late additions weren’t coming through. That’s why I bought the hopstopper. After using it I have noticed that hop flavor and aroma does come through more. I like to let the hops roam free in the wort, but I need to find a solution to minimize trub as well.
I’ve tried whirlpooling but apparently I don’t know the proper technique. It never forms a good cone in the pot. I’m doing it manually, maybe I need one of those whirlpool paddles that hook onto a drill.
I brew lots of NEIPAs, haven't noticed any lack of hop flavor and aroma or lack of bitterness. These are 5.5 gallon batches in an 8 gallon induction powered kettle.
The hop bags I use are fairly large (9x22"), roomy, thick material with a fine mesh (LD Carlson). Only some fine dust makes it out which settles with the kettle trub.
I use about 4 oz of hops max (mostly pellets but sometimes flowers) in each bag. I 'massage' them using a (wooden) cooking paddle during the boil every 3-5 minutes to refresh the wort inside for better extraction. For the same reason, I also lift/drain them (without splashing) every 5-10 minutes. They're held to one of the kettle handles with a bulldog clip. I can still close the lid during chilling and whirlpooling.
A few years ago I built a 10-12" 'hop taco' very similar to your hop stopper, but without the divot in the middle and a much lower profile. Although it worked the best of everything else I had tried before, when pumping, even at lower rates, hop matter still sucked tightly against the mesh after a while, restricting or even stopping flow. It gets a green felt-like jacket.
Since I started using the bags, about 2-3 years ago, brewing (mainly recirculating and chilling) has become a true joy, instead of the bothersome chore it had been since 2008. The whirlpool and chilling phases work as they should, at full pump speed (March 809 pump) through a 1/2" bore all the way through, until it hits the narrower whirlpool nozzle to create velocity. My 'whirlpool port' repurposes the otherwise useless thermometer port halfway up the kettle. Glad to have found a good use for that too.
Using mechanical means to create a whirlpool could work, but if there are any obstructions in your kettle, the whirlpool cone of hops won't happen or not very well, due to friction.