I have a recipe for New Orleans style bar-b-q-ed shrimp. Now, that ain’t barbecue as most think of it. It’s shrimp in a Cajun spiced stock, rich with taste.
But, I start with shells from shrimp/lobsters, etc. Boil 'em for an hour with lots of other spices/ingredients.
I envy you being able to get them. I can’t here in Akron.
While I don’t know about lobster shells, an episode of America’s Test Kitchen tested making shrimp stock from shells and found that 5 minutes was optimal. I have a similar recipe from Emeril Lagasse for BBQ Shrimp and Grits, and I’ve adjusted for that. As I tend to make it months apart, hard to tell if it has significantly improved.