Ray,

You can find information about tenting vias in IPC-2221 Generic Standard on
Printed Board Design, section 4.5.1 Solder Resist Coatings. It does indicate
that the maximum size for tenting is 1.0 mm for Class 1 and 2 and 0.65 mm for
Class 3 equipment. The tenting acceptability for larger sizes should be
discussed between user and supplier.

Regards,

Gary