Sizing up a foil when proning vs towing

im 85-90kg, and im prone foiling and towing reef breaks. for towing, i can ride a code 850 if its 1.5ft+.
But for proning, I may want to ride a 980 instead because it pumps better and im guaranteed to link several waves or if its onshore wind, etc… What happens if Im proning a 3ft+ wave, which would be suitable on the 615s for towing. I would then use the 850 as the 980 is too much. I put the foil all the way back in the tracks so the takeoff isnt too hard.

Do you guys also size up when proning vs towing? I know a foil driver who was using a 980, but the waves were all 3-4ft+, good for a 615, so not idea, but he needs the 980 to get up and save battery. Its kind of like me sizing up the foil for proning.

We tow a lot and use the biggest foil (Spitfire 1100) we think we can handle so we can pump/combo and use a 90cm mast. Once it gets overhead, we go with the Spitfire 840 because it’s more of a survival issue versus pumping. We are using the Armstrong WKT 122cm with a 1 degree shim. The board has too much rocker so the shim is needed to level your feet when pumping.

Here is a small tow day with the 1100: