Originial Question: 3 tie outs per side Vs 5 per side.
Many folks like having the option to use additional (5) side perimeter tie outs in case of very high wind or sometimes for pitching the tarp "interestingly".
In general, I think that the corners and ridgeline will, and should for shape and tension dynamics , always take more force than the center perimeter or intermediate perimeter side tie outs.
If you follow that logic, AND you are going to carry more than 8 stakes for a Solo tarp then it may be more helpful to double stakes at a corner or ridge line before adding a fourth or fifth stake to a side.
I would add a center side perimeter stake, the third on a side, any time above about 10mph wind.
More commonly in high wind, the issue is a stake pull out but very rarely (I've only heard of one case) of a whole tie outs ripping off in a high wind. One reason to only use one stake/line to one tie outs. If one stake (or tieouts) fails it does not effect others as much.
Of course, for absolute strength in really high wind, more is better and that may mean carrying more stakes and doubling them in spots or carrying bigger stakes for corners and ridge lines or the use of heavy found objects for some stake points.
The extra tie outs can sometimes help reduce flap or hum in high wind. This may be the biggest plus of using all five....
What do I do? I usually carry only 6 or 8 stakes for a Solo tarp and find stake out objects or a more protected site if I expect high wind.
On a Duo size tarp, the five per side is more helpful since the tarp is much larger and the wind force on the side starts going up fast as the tarp size increases.
Side Panel Tieouts:
On lightweight tarps or shelters with side panel tieouts (in the middle area of a panel or side) I advocate using a short bungee loops tied to the guy line to help limit the force on that spot.
I also suggest not over tightening that point when staking; rather stake it out until it gives an initial gentle pull on the spot vs. pulling the tarp/shelter side out very far.
If the the side is pulled out very far to make lots of nice and pretty extra interior room, then that point will get a LOT more force on it compared to a side or even a corner perimeter stake point. (Well reinforced and heavier Silnylon side panel tieouts can be pulled more than a lighter Spinnaker/Cuben )