Elliott Gray's D-rig advice...

This isn’t something I have used in the past but I can safely say that when using something like IQ2 straight through to the hook, you’re better off with a short Hair. I am big fan of long Hairs but it’s crucial for the rig to have a lot of movement and flexibility, which a fluorocarbon hooklink will drastically reduce. If I were to use the rig you have mentioned, in the scenario you have mentioned, I would aim for a hooklength of around seven-inches – that is as short as I would ever really like to go.

The hooked-to-landed ratio was spot-on with the D Rig presentation

As for a Hair length, I would consider trying a D-Rig presentation, which is something I like and have played around with in the past with great success. I used Hybrid Stiff to construct my D-Rigs but you will be able to tie the same rig just as effectively, and more easily with the 20lb IQ2. The great thing about the IQ is that it appears invisible in water too, and the only reason I used Hybrid Stiff instead was because I was snag fishing and always prefer a coated braid in this situation.
I never dropped a fish on the rig I have shown here, and I would certainly advise giving it a go with your IQ2, as just like
you, I was fishing over a hard clay bottom.