I've posted some screen grabs from
Up the Sandbox to my David Selby site:
http://www.ldrservicesonline.com/davidselbysiteI posted some more info about the DVD release last night on another thread, but I think that thread is currently unavailable, so I'll summarize briefly.
While Streisand doesn't specifically mention Selby in her commentary, the DVD also includes feature-length commentary by director Irvin Kershner, and he does mention Selby a couple of times.
First, he briefly mentions that he was cast because they didn't want Streisand surrounded by superstars in order to make her role as a housewife more believable.
Second, he discusses David's timing/rhythm and how expressive he is with his eyes in the scene in which Paul brings Margaret breakfast in bed and they talk.
Of course, if you want a lengthy discussion of which side of Barbra Streisand's face is her better side, then her commentary is the one for you. (And I really wish I were joking, but the fact is she does go on and on about it.)