We can take a small IFR and a small IAB and get the same fueling at idle as a larger IFR and larger IAB. The difference will be how they continue to carry fuel through the top of the transition. So if someone says they have had success using an IFR, IAB and a transition slot restriction, we can't take the IFR/IAB and expect it to work without the transfers restrictor.
Hope this makes sense and is of some help.