With the Antron 99 being a fullwave on 6m, this would present some problems. One, it would have a very high impedance on 6m. Another fact, it would also put most of it's radiation up at around 30 degrees. Once you get longer than 5/8ths wave the pattern starts to go higher, not lower.
If you want a dedicated dual band vertical for 10m and 6m. I don't know if you want another antenna for just 6m, or to have one antenna and one feed-line. If you want one antenna and one feed-line, you can do like I suggested before. That is, you just make parallel antennas. You make the 10m vertical out of some kind of tubing; you make the 6m part out of wire; run it alongside the 10m vertical, and space it about 3" from it using insulators. You also need to make 3-4 radials for both bands. These, too, can be ran parallel to each other. For the radials, I suggest using 300 ohm ribbon wire: you just cut 3-4 radials for 10m, and then cut one side of the ribbon wire for 6m. When you cut it for 6m you just need to make a 1" gap in the ribbon wire on that side.
I hope that helps.
73, John, AD7VH, east central Nevada