Shared Photo Streams - problem with Aperture 3.4.1?

I've been trying to add new photos to an *EXISTING* Shared Photo Stream using Aperture 3.4.1 but it won't let me ...

I'd like to review and edit these photos with iOS apps on my iPhone or iPad before I share them online through Instagram or Facebook. I figured using a Shared Photo Stream to selectively share photos with my iDevices would be just the thing.

The Error Message

A dialogue box window slides down telling me the supported file types (JPEG, PNG, TIFF and RAW), and that my photos "... can not be uploaded because they are not supported formats or they are too big."

I shoot in RAW and edit these in Aperture no problems. Then, from what I read, when you upload a RAW file (large!) to a Photo Stream an optimised JPEG is created and uploaded (smaller, and much like when you sync photos from your PC or Mac to an iDevice through iTunes). But this isn't happening.

Aperture will let me upload the same photo files to a *NEW* Shared Photo Stream - so this is more of an annoyance at the moment ..

I just wondered if anyone knew of a workaround? Does anyone have a better way of sharing photos between their Mac and iDevices?

Appreciate any help or suggestions.