I have a 4" steel pipe (11') that I want to use as a clothesline post. The soil is well drained sandy soil with winter freezing (Ottawa), and I plan to set the post in concrete. My current plan is to set the post in "Post-Mix" (quick setting) cement in a 4 ft deep hole about 12"-15" diameter hole with 6" of gravel for drainage. My biggest concern is not to have a pole that is leaning in a few years due to a constant load in one direction, especially considering how easy it was to dig the hole by hand. Are the hole dimensions appropriate? Is "Post-mix" the right mix for the job? Is there something else I could be doing?