I have just put up a shade sail to keep the sun of the front of our west facing rental home.
I just thought I would mention a trick I learned some years ago for making sure support poles ( CCA logs ) stay in place.
Rather than mixing concrete or using the rapid set mixes it is much cheaper and faster to just add cement powder to the soil you have dug out from the post hole, make sure the soil is just damp if it is completely dry add a tiny amount of water not enough to wet the soil just so it is like any good garden soil.
Mix the concrete soil mix to about 5 to 1 to about 10 to 1 soil to concrete enough so the soil looks grey and is covered in concrete is usually enough.
Then put in your pole and refill the hole with the mix ramming the soil concrete mix down well with a flat ended crow bar or other heavy flat ramming tool.
Add a few shovels full pack down untill solid and then add some more and repeat untill the hole is filled.
The advantage is you do not need to hold the pole for longer than it takes to ram down the first few layers of the mix and the pole is stable enough to use immediately. The mix will harden over the next few days but is usually firm enough to carry most uses like shade cloth etc.
This does not work in very sandy soils but will work in almost 90% of soil types.