Jackie, followed your instructions and got negative results. The cover view in Calibre is OK for every book (with a white cadre around it). As mentioned above M+RP said:
"hi, I'll update the book information dialog (or edit book information dialog) in next version which you can click the thumbnail cover to show it in full screen mode directly".
Don't know whether that will do it, but we'll have to wait and see. The funny thing is that with the smaller cover books M+RP "tries" to give me the full cover, but then immediately goes back to small(er). It looks like the culprit is M+RP. Walt above says that he has no problem with Aldiko reader, giving him the full screen. I installed Aldiko as well and so far have just got a complete blank for every cover. Maybe we'll have to wait for M+RP's next version. Thanks Jackie!