quick question...

i am making an 8, 12, 16 square tiered wedding cake tonight and decorating tomorrow. The 8 inch tier is going to have strawberry preserves in the middle and the 12 inch tier is going to have raspberry preserves in the middle. I have not used preserves with such a large cake yet. I want to make sure and put enough in so they can see and taste it but not too much in. I am nervous of the preserves making the two layers slide....is that a fear that could happen or am I just thinking it up? Please help me figure out how much of preserves I should put in between the tiers and if there is anything extra I need to do to make sure the tiers wont slide or do anything else because of the preserves...thanks so much!

April :0)