Not building another one mate. This sucker was over 200kg. Virgs and I could not lift it ourselves. Yes the gussets could have been all the way along but in the end this works well. Wind is more of a problem that I have found. Although not checked this since I worked on the worm gear slop.
With regard to the MPA though. I don't really think it will make much difference. Like Rally said, the extraneous noise in the system is more likely in the weakest point and that is most often not in the pier or footing. Most people over engineer those two things because removal is a problem. Screw fixings and connections is where most of the noise comes from in the end. I specified my MPA but just checked slump for water content. I figured that water content will finally decide what the final mpa will be when cured. Not that I could really do much about it once it was in the hole.