Anyone had any experience of the Isabella Shadow Canopy?
Many years experience; not sure I understand your problem though. My Shadow pegs are the massive ones that came with it, plus three more I purchased, hard to credit anything pulls these out?
In windy conditions I put two guys on each pole, one to tension outwards [90 degrees to van] each corner, one to tension longways. For the centre I place the two guys at 45 degrees to the sheet front edge so there is 90 degrees between each of these two guys.
In addition I place the pole bases outwards so the pole slopes with the top nearer the van than the base.
I rarely fix the bases, but have sometimes done so with a rock peg through the plastic foot's loop; make sure the pole base is further out from the van than its height, as no way if it throws a pole don't I want it to hit the van side. Seen elsewhere the result of that.
In really blustery conditions I take it down, more because I can't stand the noise and buffeting. Quite typically just remove poles but leave pegs & guys in place and put the cloth in the car to readily put the Shadow up when things are calmer.