Hello and welcome Mumof and Bobkate 
Good luck with the shredding Mumof. You will ache like buggery for the first few days but it soon passes! Try and measure yourself before you start (tape measure rather than scales) and you'll be amazed at the results...
Bobkate well done on getting through the Shred. Isn't it great to see the improvements? I'd agree with notyummy that Ripped and Banish Fat Boost Metabolism would be a good combination, particularly if you get occasional back problems.
And speaking of backs... aw getorf, poor you
. Just take some time to rest up and don't think it will undo all your good work, it really won't! Make sure you lighten up the weights for a while after your back's better. When my lower back suffers, I'm sure the weights are a major factor in exacerbating it. Hope you're on the mend soon.
L2 Killer for me today. For me, it's the hardest of the 3 levels in Killer. The end of the last circuit, lateral jumps immediately followed by star jumps (and that's after jumping lunges a bit further back), leaves me cream crackered! And 1-legged burpies in there too, anyone for 1-legged burpies lol?
Hope everyone else is doing okay. Very inspiring reading at the moment this thread!