MLPPP Overheads and ATM Frame aligning

I'm looking to optimise the following:

MTU
MRU
MRRU
Incoming MSS
Outgoing MSS

I understand the concept on a single link connection but MLPPP confuses me and I don't completely understand how packets behave over 2 links.

Could anyone share their knowledge for me to get the MTU optimally for 2 links?

I wouldn't have thought TCP/IP settings have any relevance (but my network knowledge is poor).

Have a look at http://www.tcpipguide.com/free/t_PPPMultilinkProtoco...