They "aren't going to let me bill them to have my employee watch someone" else do the work, he said.
In May, four of six unions signed a Customer Satisfaction Agreement, a set of new work rules designed to streamline operations and give exhibitors more leeway in setting up their booths.
The two other unions - carpenters and Teamsters - signed, but not by the deadline imposed by the SMG, the private facilities-management firm that now operates the center.
Their work is being done by other unions. Union stagehands and laborers are handling most of the work formerly handled by the carpenters.
"You are going to have [inexperienced] labor in the booths, and my clients are going to pay for their learning curve," said one contractor, who didn't want his name used for fear of creating bad relations with SMG.
"We're stuck in the middle," he said. "We don't want to be in this position."
Lorenz Hassenstein, who oversees day-to-day operations for SMG, has heard these complaints. He has two responses:
One is they are only partly true. Yes, different workers are handling the jobs, but they are capable, he said. Efficiency has improved, costs are lower, and there's a new cooperative spirit at the center, he said.
Stagehands and laborers earn less than carpenters, which Hassenstein believes will offset temporary inefficiencies that may occur as everyone adjusts to the new rules.
Second, he said, it's not SMG's fault the leaders of the Metropolitan Regional Council of Carpenters Local 8 didn't sign on time. (The leaders say they did.)
The carpenters' union leaders and the contractors are "trying to figure out how to get the union carpenters back in the building," Hassenstein said. "That's their agenda, and I understand that."
Union carpenters handled 166,000 work hours a year at the center, some of them through employers such as Pack.
Like everything having to do with the Convention Center, the issue is complicated, partly because the convention business itself is complicated, with a lot of intertwined interests.
Organizations book space at the center for their conventions. Many include halls lined with exhibitors' booths. That's where companies like Pack's get involved.
Known as exhibitor assigned contractors (EAC), they are hired by exhibitors to build their booths.
"Exhibitors' rights" - leeway given to exhibitors to build their booths - were at the heart of the new work rules. Exhibitors who wanted to set up their own smaller booths themselves instead of hiring union labor benefited from the changes.
But some booths are larger, and some exhibitors don't want to do the work. Some also set up the same booths at multiple conventions over the course of a year, hiring the same EAC crew, which travels with the booth.
Many EAC companies employ union carpenters because union carpenters work in many unionized convention centers.
But not in Philadelphia, not anymore.
Until the rule changes, Pack's company, AE I&D, a division of Arata Expositions Inc., in Baltimore, employed a steady crew of about a dozen union carpenters, including Pack's daughter, a union carpenter from Delaware County.
Contractors now have two choices, EAC managers say: Walk away from the Philadelphia business or cut out their experienced employees and contact SMG to hire union stagehands instead.
Pack said he was turning away Philadelphia business because the cost situation is too unpredictable.
The two other contractors, both local, are trying to figure out their next moves while staying on the good side of SMG, which now dispenses labor at the center.
One is trying to increase his business in other cities, even though it means more time on the road for his employees.
The other is using his longtime union carpenters in his local exhibit-repair shop. But he worries that the work will run out and that they'll have to be laid off.
"I knew it was going to be a problem," said the contractor. "I didn't know it was going to be as big of a problem."