Question:
If I add additional baggage after the first (and only) flight of a trip on carrier A, will the fees and limits be based on carrier B?

Also if someone could let me know if I am on the right track here it would help me a lot. I am new but try to find answers myself. It isn't easy; since I live in South Sudan internet is expensive and I often don't have electricity.

Background:
I will be flying back from US to Uganda in Aug 16th and I am planning to book on Brussels by transferring AMEX to Aeroplan miles. Against my nature, I decided I might as well book business class since it will allow me more checked luggage and I can book extra 32kg bags for only $160 each.

I won’t be traveling from my home airport because of a small conference, but instead from SW Florida where my grandfather lives on Aug 15th. I intend to fly the night prior and meet a family member with my baggage at Dulles (nearest Brussels hub). I’ve realized that I might be able to combine this booking so that I won’t need to pay the $160 for a flight from SW Florida to IAD. Also I guess I would be able to have more baggage and sit in front of the plane on that first leg... Will I need to book the last flight of the day for this to be considered a layover (it will be under 24 hours)? Also I can’t imagine it would be possible to find the combination on the award search so do I just find the flight #’s and book this by phone?

So again assuming I can book this, will I be able to add my extra bags at Dulles for the price advertised by Brussels? Also if I check any bags from SW Florida will I be able to remove them? (I may need to repack or I may bring something for my family if possible) Can the new bags be checked in the night prior?

Thanks in advance!

Scott

By the way the bags are in SW Virginia so bringing them to Dulles is not a huge deal