Ice cream shop percentages, insights?

Hi all, I run a couple of QSR's, opening a new one in June. I have been approached with an opportunity to essentially franchise a store for an up-and-coming local ice cream brand in the space directly next door to my new QSR project. Ice cream is complimentary to our product and the brand is locally very strong. This is the first attempt at a retail store for the brand so they don't have any real good financial data that I could benchmark from and I have only a vague idea of how I should be projecting the financials from my QSR experience.

Anyone run an Ice Cream/Novelty store? Do you shoot for traditional 60% prime cost (30% labor, 30% COGS), or is it more along the lines of retail? In our area it will certainly have massive seasonal fluctuations with 4 months of the year being cold, how much (%) busy season revenue do operators bank for the slow months? How much slower are the slow months? What's a good profit margin to shoot for? Any insight would be appreciated!