I have a pair of 288c drivers and need horns.My issue is space so the larger multi cells wont really work as they will be sitting atop of a pair of 612 utility cabs loaded with 515bs (which is basically 18" deep)..I know its a bad idea to use a 511b or 811b with an adaptor or just drilling new holes..I was thinking of modifying a pair of 511 to a 511e but before I alter horns I thought Id ask ..any ideas staying within the altec line would be appreciated...thanks in advance