Topband: Interaction

[Clive GM3POI]

I have an 80m 4SQ around my 160m Vertical and when I'm on 80 I short the 160 
vertical to ground. I know that because my 160 vertical is top loaded that 
the loading wires interact with the 80m 4SQ. Could I minimise that 
interaction by base loading the 160m vertical to send it LF when on 80m. 
Also making the top loading physically as small as possible should lower 
interaction.
    I realise that the real answer is to either have a stand alone 4SQ or a 
full size vertical on 160. Any ideas? 73 Clive GM3POI