If you have the horizontal room (70 feet, sounds like you might) and
at least 35 feet up, why not a Half Square for 40? Doesn't need
radials, it's an 'upside down' phased vertical array with some gain
and a good TOA. Be aware however, it is somewhat directional. Easy to
make on your own, also cheap and there is a lot of info on the Web.
I have one for 20 meters (very modest with the antennas here) and it
works a lot better than my R5 vertical and full sized G5RV.