I though that smaller pkts help voip for low jitter and less delay. Ill give it a try and post results here.
Queue size is the maximum number of packets that the queue can have. IT IS NOT the packet size. Packets that come into the queue in excess of the queue size get dropped, and therefore do not consume any more cpu resources, and do not add more to latency. You should give high priority (low priority value, like 1 or 2) to voip queues so that they get processed more quickly and therefore do not get very long, and choose the lowest queue size that results in very few dropped packets. You should give lower priority to non-voip traffic, and a much lower queue size. That way, when there is a lot of non-voip traffic, the non-voip packets get dropped, and need to be re-transmitted, thereby not clogging up the queue processing.
It is like when there are a few lines at the bank, all going to the same group of bank tellers, and each line is for a different priority level of customers: Let's take the simplest case of 2 priority levels. One line is high priority, and those customers can use the first available bank teller, but every nth customer must yield to a lower priority customer. The other line is low priority, and they can use a teller only when there are no high priority customers waiting, or after every nth high priority customer, whichever comes first. If you consider this for a moment, it becomes obvious that It is beneficial to the high priority customers to never get dropped (not allowed into the bank). It is also beneficial to the high priority customers to have the low priority customers get dropped. When and how exactly to drop, and the value of "n" is highly specific to your circumstances, and up to you to configure.
Kind regards