So, my recommendation is 3A/B and 4A/B, or the same on the other side. No idea where Barbados is relative to your seat. Under it, probably...
I'd recommend 3JK and 4JK outbound (or 4JK and 5JK if there are 5 rows in the forward cabin) as the sun will be shining mainly towards the AB side.
Also when we flew in March, BGI was initially on the right hand side of the aircraft, but thankfully was indeed under the aircraft just before we landed