Hi Marty, I also have a 16" f/4.5 and here are the eps I use: 40mm Pentax XL, 27mm Panoptic, 16mm Nagler T2, 9mm Nagler T1, 7mm Pentax XL, and a 5.2mm Pentax XL. All perform great and have good edge correction in my scope. I really like the Pentax's and am thinking of replacing the two Naglers with a 10.5 and 14 Pentax; I also love the 27 Panoptic.
I have a 16" F4 dob and am very happy with the following eyepieces: 27 Panoptic, 17mm T4 Nagler, 14mm Pentax XL, and 10.5 Pentax XL. I just bought a 7mm Nagler T1 and am anticipating a "trial run" when it arrives and skies clear. Note, be careful to not get too low power of an eyepiece. You will start to see the secondary in your FOV. I used a 35mm Konig a few times and the shadow of the secondary was very annoying on bright objects! The 35mm Panoptic might do the same in your 4.5 scope, so maybe try before you buy.