You don't need to reduce the height of a 4' plant to 1 1/2' by deadheading, just removed the dried flower heads only at the base of the faded petals. Next years growth buds will appear in the leaf axils (where leaf joined stem). You can shape your plant when those buds begin to swell in Spring and you can see where to make cuts if shaping is needed.

First dry day we have I will probably remove the old flowers from my own pee gee, not Pinky Winky and many years old - or I'm finding the flower heads blown around to be picked up after winter storms. Any major pruning or shaping I will do earliest Spring.

Thanks for the reply .I have been really watching it during these rain storms and its taking them really well even with the flowers on. I was afraid the weight of the wet flowers would bend it over . I had to weigh the whole plant down with big rocks to keep it from coming out of the ground with our big winds but the stems arent bending over at all. It hasn,t made it threw the winter yet but this appears to be one sturdy paint.

You can leave them on for winter interest. I think they're quite striking, personally.

unpro, not nearly what I would call striking laying on top a dwarf boxwood border, plopped in the middle of black ophiopogon 'nigrescens', clogging up a gutter/downspout or plastered to the side of my car. :) Nothing as messy like a wet storm off the ocean....

I do leave the flower heads on macrophyllas most years.