Building an organic T shape

Thanks. The method using patching seemed like the best bet at first, but after trying it the patch doesn’t seem to actually match the surface curvature. Any tips here would be appreciated

The method that involves building up distinct surfaces (Render Rage) seems more promising, but I can only get as far as constructing a few of the initial surfaces before I’m not sure how to go about making the interior. Anyone have a good understanding of this?