Two-row date labels with custom labels

[ClaireO]

I am having trouble getting my custom labels to go to two rows. The data that I am plotting is an average over two year periods, and I have labels every five years. I want the labels to include both years, and to do this I have made custom labels using the following code:
smpl 1976 1976
alpha y2 = "1976-1977"
smpl 1981 1981
alpha y2 = "1981-1982"
smpl 1986 1986
alpha y2 = "1986-1987"
(etc, up to 2011-2012)

I then applied that y2 alpha as the custom label on the graph using this code:
template1a.setobslabel(series) y2

I have tried to force it to be a two-row date label, but this is not working:
template1a.axis(b) duallevel angle(0)

Is there another way to get a two-row label? At the moment, it is very hard to tell which ticks the labels correspond to.