The ownership of property is usually the best way of proving descent in the male line. This source is useful for cottages and crofts as well as farms and larger holdings.
The best way to break into these records is through Wood's Atlas, and the related Tithe and Asylum Schedules. Part of the Atlas has been put on line by Frances http://www.isle-of-man.com/manxnotebook/gazateer/woods/index.htm
Elizabeth (then Barlow) has indexed the Atlas - see notice of the Index at http://www.isle-of-man.com/manxnotebook/famhist/v08n2.htm#58-61
Arbory has not been scanned, but, if you can obtain a fische of the Index you'll be on your way.
Anyone have Elizabeth's current address?