SQM/QOS on Wireless Broadband

I am configuring a WG3526 router running 18.06 I compiled tonight. I would appreciate some help in setting up QOS for my router where the download speeds vary between 4M bits/sec to 21M bits/sec. (Australian Wireless Broadband: atrocious service!).
My needs are that I can run my Voip with no garbling (due to low bandwidth), & hopefully my Video does not drop out.
So far, I set up using the basic SQM documentation, with 21Mb/s as about 80% of peak download & 4.5Mb/s for uploads. The reason I am asking for help is on perusing the forum, it appears SQM does not work well when the speeds vary.

There must be many people in similar varying download speed/congestion situations such as mine. If I can come to a reasonable compromise, we may be able to document the options to resolve my issue for others to use.

regards, Doug

SQM assumes that the modem will always be able to move bits out at the SQM speed. This means that on a modem that varies in speed, you must set the SQM limit based on the worst case slow, not the average or maximum. That also means that when the link is working better than worst case, SQM will still hold your user speed to the set value.

I would try tuning the upload but leave the download unrestricted.