As of 1.3.1, you can now place redstone wire on top of half slabs, however, I found that when I installed forge, I was unable to do so, it would simply just not put it there. I have tested this on the latest build (#246) with no other mods installed and it is still not working. I am unable to attach a log as a bug of this type does not give a log. I am using Ubuntu 12.04 LTS x64 and I guess I'm going to have to use ModLoader D:.