[Inkscape-user] character deleted ofter applying 'Difference'

Hello, I am trying to get some text to fit within a cone, sort of a 'sand-clock' where each letter gradually gets smaller to a point and then it increases. I do this: 1) select the text 2) Path -> Object to Path (Shift+CTRL+C) 3) Path -> Break Apart (Shift+CTRL_K) Then for each charecter with hole in them select the interior and the exterior and apply Difference. Here is the problem, on some characters such as CAPITAL 'A' or LOWERCASE 'p' when I select it and apply the Difference (CTRL+-) the character is deleted. What am I doing wrong? Thanks Norman