The tuning will change when you put it up at it's final height. Tuning an antenna, especially a dipole or any other horizontal antenna, 5-10 feet off the ground and then installing it at 30-40 feet or whatever usually results in a lot of :headbang and some .
468 devided by whatever frequency your wanting (468 / 3.940.0) it for is a starting point then trim the ends if need be but an external tuner will work wonders and give more range of coverage.
OK. :headbang
I'll just wait until the weather is fairly nice and spend the time necessary to get it right.
Thanks,
John