Plumbing return pipe in baseboard

[DaveM]

I was looking at SlantFin 30 baseboards yesterday and read that the return pipe could be run within the baseboard enclosure itself. This is appealing to me because it would eliminate any return piping having to be on an outside wall. My questions are:
1 - Is this a good idea (to run the return pipe inside the enclosure
2 - How to do make the 180-degree turn at the end - 2 90's are too big to fit into the end enclosuer
3 - How should the return pipe be secured to the enclosure.

Any other comments/tips would be appreciated.

Thanks.
Dave