You can do it, its just an extra step.
Project the wires of the lettering onto the surface of the tube.
Then you create a solid from the projected wires
(that's a few extra steps)
then boolean the new letters from the surface.

Mike Fitz
www.3dartz.com

there is a free download for curving text www.deskam.com go to downloads then {"desk engrave" it's free hope this will help it will save as a dxf or g code

the only detail is that you can't put it inside Moi :)

After you project the letter curves, if you trim your original surface with them, you can extrude the new letter surfaces using *Set dir* , *Cap ends* and *Both sides*
to create a cutter that will boolean out from the original object at a consistent depth, while following the contour of the surface.

Excellent! I hope these kind of tips find their way into the MoI documentation :)

Ed