Here's a really easy way to to a bunch of HST's at one time and be accurate.
http://www.blockcentral.com/a-halfsq...glepaper.shtml
Works like a charm!
I know its for a 1", but if you print off and increase your printing by I think its 150%, it'll make them the correct size.
Here's a chart:
http://www.thequiltedsnail.com/scale.html