Am putting a sip addition onto existing home. Sip section measures 28'W x 25' 5" L.  14"x 6" parallam ridge beam is two piece, butted and joined atop central 6"x 8" vertical post with "T"  gusset plates that will also attach to said post. Span to joint is 12'6".Had planned on using1/4' cold roll plate for gussets, was wondering what bolt pattern and size and grade of bolts would be recommended. Would bolt holes near top part of gusset need to be elonated to allow for deflection? Could someone direct me to a site providing construction details for gusset plates for parallam beams.
                                      Thanks

deflection in the beam will occur regardless of gusset holes,
There is no one-size fits all gusset plate , you need to consult an engineer who can assess your site specific needs

I agree with Chris. There are many variables you have not outlined in your post. You should consult an engineer. However, you could look through the 'Simpson Strong Tie' catalog. They have heavy duty beam to post connectors with fastening specs.

http://www.strongtie.com/