I would expect somewhere around 3' in Zone 5. And 5' in my neck of the woods since my growing season is so much longer. I checked the PW Website and it said:

Garden Height: 36 - 60 Inches

Spacing: 36 - 60 Inches

Spread: 36 - 60 Inches

Would these maybe hold a better or longer pink that regular Quickfire?

Mine seems to go dull beige much too quickly and while I like it in the spot I just wish it held it's color better.

cearbhaill, your issue with regular Quickfire not holding color may well be the site being either too hot or too dry. Luis frequently remarks on H. paniculatas that in too much heat or sun lose color quickly. My regular Quickfire stays a rich deep pink for 2 months until we get a hard frost after spending the month of August moving from white through various shade of pink. It blooms white for 4-5 weeks beginning in late June.

I'll try to keep it watered better this year (last year was a bust as far as attention to garden) but not much I can do about the sun :)

Thanks for the info!