Hi and welcome.
Being of a slightly 'bulky' build as you put it, the Biker Scout or Snowtrooper will probably be a better option for you anyway, instead of a Stormtrooper.
Although Stormtrooper Armour can come in different sizes, they don't differ that much, and some guys with larger builds can struggle to make the pieces fit them properly.
As the Biker Scout and Snowtrooper have more 'softer' parts to them, it is easier to make them fit any body shape.
I reckon these are a great choice for you.
We have a few biker scouts and Snowtroopers in our group, who should be able to help you out.
There are also specific detachments with lots of great info to tell you what you need.
Next time someone has an armour party, or next time we're trooping, come along and meet us, see what we do, and ask lots of questions about how to get yourself a costume.
Bunnies..... The cutest things ever!