Hamax rear child seat

Dec 4, 2008
169
3
38
Tokyo
#1
Hamax type child seat (fits to seat tube)

am I correct in saying that there are various fitting kits for these, i.e., if I had a kit for my hybrid style bike previously, it won't neccessarily then fit a mamachari?

is the angle of the seat tube/ clearance of the rear tyre, the deciding factor?