The grp waffle boards wont be of that much use, remember O level physics? surafce areas/pressure n all that jazz? If you add up the total surface area of the grp 'grid' on the grates it probaboly dosnt differ too much than the total footprint area of the tyres. They are of no real benefit in soft stuff tbh.
Have you so considered tyres/tyre pressures? tyre widths? wider tyre with lower pressure is going to give a larger surface area/footprint therefor givving an overall lower PSI of van/ground. make sense?
I wouldnt bother too much with mats tbh either if its just for uk beaches. Going to be fairly comapct sand overall. Without looking at daily tides/water content too much , if you compare the densit of the sand to desert conditions its fairly 'settled' and dosnt shift too much in comparison and will have a much greater density/'hardness' than dunes.
Not forgetting rule #1 though
I *guess* your recoveries are pretty much planned so you have the advantgae of being able to walk the course first to choose best route. If at any time you think its too much etc and an emergency than call the pro's out. No point in becoming an extra casualty/concern to any ongoing incident.
If its the 'big quick tides' that concern you, then dont go on the beaches! Make sure you have done on ususal stuff ie first hand local knowledge of beaches/tide books etc etc
Just my two penneth. Dont profess to be an expert but like to think i have fairly sound experience gained from driving offroad both on green lanes and more 'techinal' surfaces both in the uk and abroad.
