You could well be right - the hybrids seem to have a range of leaf morphology, this one has very low number of leaflets per leaf and is like A. baileyana in that respect, but the leaflets are less crowded than i would expect in A. baileyana.
Barb it is not possible to frill a horizontal stem plus we can't cut into the surface on the ground; best would be chainsaw; however, because, unlike other parkcare groups, we don't get field support, the best we can do is cutting the main branches and paint with glypho plus hack into the stem and fill with glypho where possible.. and hope for the best... I will add this to my gpx file of missed woody weeds - I'm still collecting.