Adding two question to the Registration form…

As my title says, I’d like to add two questions to my Registration Form that Insert to my MySQL database. I use a User Management plugin, s2member, to manage subscribers, and it’s just about perfect for my needs with the exception the custom registration fields it creates produces serialized data. I’m having a hard time dealing with that data.

(Any time I ask for help with serialized data that WordPress produces, I usually have to argue through, “Why did you write it to do that?” — I didn’t.)

I’m sort of worried if I use a plugin, it will be a touch bloated and not work well with my s2member. I’d just like to know what hook to link into, if it exists, where I can place a couple of questions. Is it wp_register?

I’ve already added the columns in the Users data table. ??