Are you SURE that the bog is due to the secondaries opening? Is it possible that the issue is with the primaries? Have you tried unhooking the secondaries? Have you tried locking the secondaries to open manually with the primaries?

I suggest all this to try and have some impact on the bog, for better or worse. And to verify that you are blaming the right culprit. Once you can impact the bog with a specific action, you know what area to concentrate on.

The idle would seem to be an easy fix with a smaller IFR. And the cruise is usually acceptable around 14 and you know what to do to dial it on in since it responds well to your changes.

A quick and easy way to test an engine's response to a smaller IFR is to insert a strand of wire stripped from a piece of 16 or 18 guage wire. I usually use one piece 2 or 3 inches long to go from one IFR to the other. It's easier to handle and can't get lost inside the carb.

Try as small a strand as you can find because it doesn't take much on the IFRs to make a big difference. Even .008 or .010 will probably be too much, but it will verify that you are doing the right thing.

The wires can be used in most any bleed or orifice to experiment. Right now, finding what impacts your bog directly is job one.