BC895XLT Master osc adjustment ?

[phbrush]

I have recently replaced the 455 khz ceramic filter in my BC895XLT with a narrowband unit in hopes of extending the life of the receiver. Problem is the reference oscillator won't warp enough to center the receiver in the middle of the IF passband, which wasn't a problem with the OEM 15 khz unit as the error wasn't a problem then. There is an adjustment hole in the shielded part of the receiver, but even when at the end of its range it's still 2-3 khz too low. The shield won't come off even after the attaching screws are removed so I can't tell if there is a cap I can remove or change value of. Is there a secret to removing this cover ? I am concerned that Uniden may have placed some of that black potting compound under the cover before they put it on. Any suggestions ?