To be fair, what PoD in particular are you considering? I'm assuming you mean one sometime around the revolution; this gets far easier as you go back farther towards the original charter. As it is, the best I could see is some sort of compromise arrangement. Say that the Virginians manage to arrive at Fort Pitt in greater numbers than the Pennsylvanians, enough to make the land truly disputable. Philadelphia would be practically impossible; it was the largest city in the colonies at the time of the revolution; there's no way that Pennsylvania would cede that to Maryland in that time frame.
And, instead of the capitol being established to the south, have it established in Pennsylvania. Since the Southerners didn't manage to get what they wanted in terms of the capitol (especially in view of how much influence Pennsylvania would have over the new capitol city) it is agreed that Pennsylvania will relinquish claims over both the Pittsburgh area along with the Maryland claim west of the Susquehanna (just eyeballing this right here). And, perhaps in recompense, Pennsylvania may get a larger chunk of New York than OTL or perhaps even some of Connecticut's western reserve. (or Pennsylvania could be kept smaller and it becomes a greater state made to serve the capitol, but I highly doubt that.
As for Delaware, you'd have to have Pennsylvania lose control over the counties and for Maryland to establish itself over them before independence. After that point, the chances of Maryland getting Delaware are ridiculously low (barring revolution et al). Although, they probably could get away with nipping at the edges.