Thanks for the reply - even if it took more than a month
In the end I bought a Slingcatcher and discovered the answer to my question myself - basically the only SD resolution I can stream at is 640 x 480.
If I want a higher resolution than that then I need to use 1280 x 540, but this is too much for my upload speed (around 1600 kbps).
Overall I'm happy with the Slingcatcher though - I can't believe you guys discontinued this piece of kit! I understand the plans seem to revolve around integrating Sling catching capabilities into existing hardware platforms, but I can't imagine how you'll come up with something as user friendly without a hardware remote, not to mention that anyone wanting such sling catching capabilities is then tied into whatever hardware platforms you decide.
Just my twopence - KUTGW