See Column F at
http://www.televue.com/engine/TV3b_p...4#.U3wXfvmSy5I
The 17.3mm Delos has a field stop 0.48" (0.25+0.23) above that of the 10mm Delos. Therefore you will have to rack the focuser inward 0.48".
I have not used the Delos range and cannot comment on their performance other than to say the quality will be similar to the 10mm Delos as you would expect from Tele Vue.