Parcorr/need more in-focus

I have a 15" F4.5 truss dob that will not allow any of my eyepieces to come to focus. I think I need to shorten my truss poles to get eyepieces to focus. Without the Parcorr, the 31 Nagler uses ALL of my in-focus...moreso than any other eyepiece I own. Any ideas on the amount I need to shorten them?

Thanks in advance,

David

Original message should read: With the Parcorr in place my 15" F4.5 truss dob will not allow any of my eyepieces to come to focus. I think I need to shorten my truss poles to get eyepieces to focus. Without the Parcorr, the 31 Nagler uses ALL of my in-focus...moreso than any other eyepiece I own. Any ideas on the amount I need to shorten them?

Thanks in advance,

David