@JohnJR : I would refer you to Article 40, Section 6 (friend):
"(friend) Employees who are in existing full-time combination jobs or who hereafter enter a full-time combination job shall be paid the appropriate full-time air rate for air driver work and appropriate inside part-time rate for the hours worked in other classifications. If an employee has no established inside rate, that employee will be paid the appropriate part-time rate in accordance with his Company seniority"
There is no 'top rate' for the inside work, that is paid at the rate you would be at if you had stayed part-time inside.
I refer to these jobs (unofficially) as Article 40 combo jobs.