You are not going to be forbidden to take more than 2 pieces , you just have an extra baggage fee, charged ..

Separate your gear into 2 duffel bags*, empty the panniers and fill the duffle bags with them and your contents

then you can take 4 panniers and have a balanced load on the road.

*Returning Aberdeen to SFO, via AMS .. my gear was in tough plastic bags used to ship grains to feed chickens,

Or as my Aussie friends called them.. Chooks..





....