I'm planning to add some PV to my inverter backup system (24VDC nominal) in the springtime and will probably use an MX-60 charge controller. The arrays will be a little ways from the house, so combining panels for higher voltage is desirable for several reasons. Given that some shading might occur especially late in the afternoon, what's the tradeoff between greater number of panels in a string and losses should some shading occur?

Also, I thought I read that some manufacturers include diodes internal to their panels so that not all the output of a panel would be lost should part of the panel become shaded. Is this true and how do I find out about this feature? There doesn't seem to be much mention in any of the literature I've seen.

Thanks!