Aer Lingus Birmingham->Dublin->Orlando questions

I have a flight coming up which is from ticketed as Birmingham to Orlando with Aer Lingus in Business Class. The flight is one stop via Dublin with a 4 hour layover.
As the aircraft operating from BHX to DUB is economy only, I believe I still get full Business Class baggage allowance; is this correct? What happens to that when I get to Dublin? Do I collect and re-check and how does this fit in with the US Prescreening for customs that they do in Dublin?
Also, I have some pretty large luggage (90 x 60 x 30)- It fits in the Virgin allowable size but I'm concerned that it is actually over that stated on the Aer Lingus site (max combined external dimensions being 158cm) - Do you know how strict they are on this? And what is likely to happen if I turn up with my existing luggage? There is no mention on the Aer Lingus site for oversized bags, only over weight.
If I try to prebook any luggage online, it tells me that fees do not apply to my booking, but baggage is subject to their standard carriage terms.
Thanks in advance for any advice or pointers
As the aircraft operating from BHX to DUB is economy only, I believe I still get full Business Class baggage allowance; is this correct? What happens to that when I get to Dublin? Do I collect and re-check and how does this fit in with the US Prescreening for customs that they do in Dublin?
Also, I have some pretty large luggage (90 x 60 x 30)- It fits in the Virgin allowable size but I'm concerned that it is actually over that stated on the Aer Lingus site (max combined external dimensions being 158cm) - Do you know how strict they are on this? And what is likely to happen if I turn up with my existing luggage? There is no mention on the Aer Lingus site for oversized bags, only over weight.
If I try to prebook any luggage online, it tells me that fees do not apply to my booking, but baggage is subject to their standard carriage terms.
Thanks in advance for any advice or pointers