I just checked the specs on the Silva you have. Decent product and it actually uses the same cells as the one I have. Powerfilm produces these flexible solar panels and sells to a lot of companies. Powerfilm actually has very similar product compared to what you have. It is all just rebranding. I almost bought the Powerfilm equivalent of what you have (it has 5 instead of 4 panels though), but want a little more power, so I ended up with this one. I can't recomend this one enough. I have charged AA/AAAs under the canopy of the Black Forest in 4 hours with the panel strapped to my backpack.

I first used Powerfilm, a much bigger model, while deployed in Indonesia. I used it to charge a laptop, Nikon D3s batteries and other gadgets. Then I started looking at what they offer to the consumers. It is the same product minus the digi cam.