I think i can help with that.. I might be totally wrong here but it seems like that VehicleUtilities.cs controls those things.
(Make a backup on the file before editing and saving so you can revert and go back)
In your server folder go to -> Mods -> Objects and open/edit file "VehicleUtilities.cs"
In that file you have these rows:
// Excavator var excavatorMap = new StackLimitTypeRestriction(true, 30); excavatorMap.AddListRestriction(blockItems.GetItemsByBlockAttribute<Diggable>(), 20); excavatorMap.AddListRestriction(blockItems.GetItemsByBlockAttribute<Minable>(), 80); AdvancedVehicleStackSizeMap.Add(typeof(ExcavatorObject), excavatorMap); // Skidsteer (same as excavator currently) AdvancedVehicleStackSizeMap.Add(typeof(SkidSteerObject), excavatorMap);
The Skidsteer is using the same map as the excavator so you need to change the 3 numbers in the excavatorMap variable.
Let me know how it went