MLP Fragmenting and Interleaving

I mainly wanted to post this here for future reference, but I labbed up link fragmentation and interleaving on PPP links tonight.  Cisco recommends this on links slower than 768kbps.  MLP interleaving determines fragment size based on the configured link bandwidth, and what you as the network admin put as the delay within the ppp mulitlink fragment statement.  For those math lovers out there, the formula is:
delay in seconds * configured bandwidth (i.e. 10ms on 128k line would be .01 * 128000 = 1280 bits/160bytes

Here was my interface configs:

interface Multilink1
ip address 172.16.12.2 255.255.255.0
fair-queue 10 512 14
ppp multilink
ppp multilink fragment delay 10
ppp multilink interleave
ppp multilink group 1
!
interface Serial0/0
bandwidth 64
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1
!
interface Serial0/1
bandwidth 64
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1


Notice that the delay is put in ms in the ppp multilink fragment delay command. Here is some interesting output:

Now the bandwidth here is configured at 64kbps per interface, with 2 in the bundle...so 128k combined.  I configured the delay at 10ms, so if we use our formula we should get: .01* 128000 = 1280/8 = 160 bytes.  But what the duece!  Why does it say right there that the frag size is 72? The QoS book says that it should be 160bytes as well.  Now I know multilink PPP will split the traffic among the lines, but I am a bit confused.  Any clarification on why this is happening would be awesome. 

Oh and btw...to clear that pesky neighbor route thats comes with PPP anyways:



C 172.16.12.1/32 is directly connected, Multilink1


just issue the no peer neighbor-route on your multilink interface...annoying.