Q-Ball, surplus supplies accumulate on their own in the base with biggest port in a given economy. If two bases have biggest ports, supplies go to the base with a bigger airfield.
Several Jap players noted that supplies dumped in Rangoon (port 4) trickle to Singapore (port 9).
-set supplies in Rangoon to stockpile. Once you have a big stash (30k), set supplies spinner in Mandalay to + 10k and stockpile to ON, and disable stockpiling in Rangoon. This should pull Rangoon supplies to Mandalay and make it sit in Mandalay. From Mandalay the supplies should be distributed to te units in field. Repeat the process ad infinitum.
-is the HQ in Mandalay a command one? A command HQ can attract 20k supplies to itself at all times. I would park a command HQ among your 9 diviisons in a non-base hex and see if it helps with supply distribution.
And read this thread.
Movable command HQ are the 5th fleet and the southern command HQ.
I tend to place the southern in Magwe for various reasons and it works well with an army comparable to the one indicated here in the thread.
Also, I never ever defend bases in Burma, placing all my guys in non base hexes and hoping for the best.
As i wrote in the ongoing thread on the monsoon, I think that off-base defence in Burma is more viable, supplywise, than in-base defence. I don't even have a precise rationale for that, I just know it works perfectly for me and has always done so.
I don't even ship much. In the last 6 months, I have shipped the equivalent of little more than 200k supplies.
Even rounding up the numbers, it's 35-40k per-month, basically nothing in the great picture of things.
I have probably way more AAs in the theatre than the ones Q-Ball has (45 in total, of which 25 in magwe)