Nicaraguan Boa there... (Nicaraguan, Costa Rican, Panamanian, etc.)
Point is, it's a central american boa. They don't get near as girthy as a colombian boa. They don't put on much weight in that way.
A healthy adult Nicaraguan may be as long as a 5' boa but will have the girth of about a 4 footer. Never getting 'thick'.
That's its nature.
I have a 6 foot adult colombian that is about 6 times as fat around as my adult cenrtral americans.
Centrals can still breed and give healthy births (considering she is mature), the litter would also be of average size, but the babies would be much smaller... maybe thinner than your pinky, in comparison to baby colombians being approximately thicker than your thumb when they are born.
Best wishes! Joe
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Thanks and take care - Joe Rollo
'Tis not the stongest of the species that will eventually survive, nor the most intelligent, but the one most responsive to change' Charles Darwin