A Q400 is 108ft long and just under 9ft wide. For a simplified (rectangular) fuselage plan area of just under 1000 sq.ft. Call it 100m^2. If you had an inch of solid ice over the whole fuselage, you'd have 2.5m^3 of ice. Ice has a density of just under 1tonne/m^3. So that truly ridiculous amount of ice would weight 2.5 tonnes.If you took a more reasonable thickness of ice, a more reasonable assumption of where it would adhere and of the real fuselage area, you'd be down in the hundreds of kg.
More importantly, managing to accumulate such a ridiculous amount of ice and not have the wings contaminated is practically impossible - you'd have to sit in freezing rain for hours, and no anti-icing fluid can protect the wings for that long in similar conditions. if you look at some typical HOT values and some assumed precip rates, you'll find 1/4" or less of ice is more what you might see.