[TowerTalk] 40-30m dipole design

[N1BUG]

While trying to figure out how to move up a notch from my inverted V 
antennas on 40 and 30 meters I came up with a crazy idea. I was 
looking at building a rotatable dipole for 40 meters, either full 
size or possibly shortened. A 70% of full size linear loaded 40 
meter dipole is nearly a full size 30 meter dipole. Various articles 
claim only about 1 dB reduction in "gain" from a full size dipole on 
40. Could relays be used at the dipole feed point to short out the 
linear loading, making a two band antenna? It seems good in theory 
but if it were that easy, wouldn't someone have done it already? I 
have no idea whether RF voltage across the relay contacts when 
operating on 40 meters would be high enough to make this 
impractical. Any comments, wisdom, or wild guesses?

Any alternative thoughts on building a 40 and 30 meter rotatable dipole?

73,
Paul N1BUG