Topband: 160 Tower on 80

[Glenn Biggerstaff]

Hi all, I have a 90 foot Rohn 25 tower with an insulated base and insulated guy wire sections for top loading ,base fed for 160 meters. It work great ,but I would like to use it on 80 meters as well.
The 3 ideas I have considered are voltage feed  at the base  with a resonant LC network  at the base, but I am a little worried about the voltages present at legal limit power. Second idea,disconnect the top loading and put a trap between the top loading and the tower to divorce the top loading on eighty then an L network at the base for 80. Third idea, run a wire as a sloper either a quarter wave fed against ground or a 1/2 wave dipole from the tower. 
Any thoughts or alternative ideas would be greatly appreciated. 

Glenn WW4B