DIMM channel question

I have a machine with quad channel, and 8 DIMM slots. The manual says to populate A1, B1, C1, D1 if only 4 DIMMs. If 8 DIMMs, it says A1, A2, B1, B2, C1, C2, D1, D2. Simple enough when I had only 4x8gb DIMMs. But now I have an additional 4x16gb DIMMs of similar speed (but not exactly the same).

The question: Do I mix per channel (8gb in A1, 16gb in A2, etc) for an even amount (24gb) in each channel? Or do I pare the same DIMMs in each channel (8gb in A1, 8gb in A2, 16gb in B1, 16gb in B2, etc). This would result in 2 channels with 16gb and two with 32gb.

Which will provide the best performance for crunching? And if the latter, does it matter which of the 4 channels gets the larger DIMMs?

It is not a given that this combination will work but it often does.

It may be necessary to set ramspeed in bios to that of the slower sticks to begin with. It might be worth comparing the secondary and tertiary timings also and setting to the lesser timings if the rig is not happy with the combination

When I have done this in the past I have always put the larger Dimms in a1 and smaller in a2 etc.