If one founder contributes the IP, should this be reflected in his shares?

IMHO, it is strictly up to you and your "partner/co-founder" - he may bring the technology, but you, I assume, bring the business/commercialization to the table. IMHO, it is basically a "wash" - meaning that both of your strengths are equally important - his technology is useless without marketing, your marketing is useless without the product/technology.

If he hasn't contributed any capital or equipment to the venture, I suppose his IP contributions might be the only thing against which his shares could be reflected. Equity split between two founders does not have to be 50/50: capital contributions can be different, IP contributions can be different, ability and availability to manage operations may be different, etc. Much goes into the calculus. It cannot be overstated that you two need to have an honest conversation about what value - monetary, intangible, etc. - you are each bringing to the table and what kind of effort each of you will be exerting to manage and support the business, at least initially. The relationship between founders and the business entity itself should be memorialized in a charter document for which you should consult a local corporate / IP attorney.