I have inherited a 50 year old home in relatively good repair except for the windows. They are original Anderson double hung. The frames are in great shape it's the sashes themselves that need painting and reglazing. Since there are 14 of them varying from 12 over 9 to 6 over 6 I'm definitely considering retrofitting. I like the Marvin tilt-pacs and am wondering if anyone has any experience with them. Any comments -pro or con- adivce etc. would be appreciated. Thanks!