My advice is, don't do it! I had one for 2 seasons. I tried the PVC pipe footing into the asphalt like the pictures above. I actually put 18" of extra pipe on the legs to lift it where my tower would fit under it without folding it down. It worked pretty well if the wind didn't get over 15mph. Also like the pic above, mine ended up flipped over a fence, torn out of the ground about 3-4 times in those 2 seasons i owned it. Each time was $30 or so in PVC parts at Home depot to fix whatever broke. Keep in mind, I don't live in a very windy area either, but any wind over 20mph will destroy these things. My tarp finally started to tatter and the metal eyelets broke, so the next big storm that came took it down for me for the last time and it went in the dumpster. Waste of $300. My boat now stays outside for 6 months out of the year under a LEGIT cover that gets re-waterproofed every season and for the winter, it goes to a relative's house where the tower is folded and it rests under a nice dry carport. I can't tell any difference in wear/tear vs. putting it under an over-glorified tarp setup.
If you do choose to get one, at least buy a cheap one so you aren't out of pocket too much and if it did work out for your setup, you could upgrade later: http://www.harborfreight.com/10-ft-x...opy-68218.html