Group item versus custom glyph

Is there an option to set the expand and extract glyph from a group item manually?

I found out that 'CellNode' contains the option to set the contract and expand glyph manual. Still it seems there is some cropping by 1 pixel going on. Is it possible to disable this cropping?

I cannot see any unexpected behavior or "cropping" here. If a problem persists with the latest version, please provide some sample source app with which this can be reproduced.