Setting link speed on mlppp member interfaces

[clarknova]

I'm running mlppp for a 2-link connection and loving it, so naturally I have to look for new ways to mess things up ;)

My two modems sync at slightly different rates, modem1 at 960/6144 and modem2 at 896/6144. By default then, my combined speed profile when using these 2 as an mlppp connection will be the double of the lower sync rate, or (2896)/(26144) or 1792/12288 effective sync rate.

Now I'm looking at Advanced Options for the link in /interfaces_ppps_edit.php?id=0 and I see I can set the bandwidth of each link independently. I'm hoping I can use these settings to squeeze out the delta uplink speed on my second modem, and perhaps exercise something closer to a nominal (960+896)/(2*6144) connection. The problem is that some things are not clear when looking at this option:

1. Am I setting the upload or download bandwidth of this link?
2. Should I set it to the modem's actual sync rate, or some lower value derived from it? I ask because there are of course factors such as pppoe and mlppp overhead that make real throughput something less than sync rate. For example, despite what appears to be an effective combined uplink sync rate of 1792, I have to set my upload limit to 1400 in the shaper to get control of my queue.

Perhaps some clarification of these points could be added to the already great ppps page in pfsense.

Thanks.