I cannot recall of one with such dimensions, considering that many hydrangeas -when kept past 10 years- will exceed their advertised height and width dimensions.

I think your right. The one planted is in it's 3rd year is over 4.5 ft. and still growing. It will be over 5' by the end of the season.
Any suggestions for another type under 3.5 feet that will survive in 6a/5b.
Paul

The City Line Series of mopheads came out for sale recently (see the link below) and appears to be compact. The problem is (also) that they recently came out. Because of that, not too many people in the forum have experience with them and the claims by the vendors. They claim it will stay about the height you want and will grow in the zone range that you require. They are available by mail/Internet.

Here is a link that might be useful: City Line Link

Pia is supposed to grow to about 3'