In Report Designer, when modifing an envelope, the only options are adjusting the margins.  All other options are grayed out. 

 

It would be very useful if all these options were enabled.

 

For example, the Paper Size is fixed, at Com-10 in my case.  I cannot select a #10 envelope, which seems odd to put it mildly.  The only option is to adjust the margins to locate the print output to match the envelope.