I am curious if this is actually legal as per the rules, as shield spikes and the bashing enchantment appear to stack when applied to the same shield, in Hero Lab. This makes the shield count as three sizes larger when performing a shield bash attack. While this was legal in 3.5, from what I understand, they're not supposed to stack in Pathfinder.
http://paizo.com/threads/rzs2kls2&pa...d-spikes-still
James Jacobs does not appear to be a fan of the combo. :-P
By all means, if I'm wrong, let me know.
On a side note, I checked the Pathfinder FAQs on this, and I was unable to find a concrete answer. The Paizo message board seems to have many questions on this subject. There was a FAQ update mentioned in the works on this subject, but it was never put up.
http://paizo.com/paizo/faq/v5748nruor1fm