The problem you talk about with not being able to transmit with the SL40, using the Skyview conversion harness, is exactly the same problem I had.
I found that the wiring on the dSub connector to the back of the intercom was not correct and I had to move some of the wires around.
To check the wiring you are going to have to pull the wings away from the fuselage to get to the access panels for the headset jacks. And, you will have to pull the cover off the avionics bay to access the intercom dSub connector. While looking at the electrical schematic you can do continuity tests to get the wiring into the correct positions in the intercom dSub connector.
rvbuilder2002 gave some good directions in a prior post. Here is a copy and paste of his directions:
Check continuity between the shorter of the two tangs on the pilot mic jack (the one that contacts the ring position on the mic plug), and pin 2 of the intercom Dsub connector.
Do the same with the copilot mic jack and pin # 3 on the Dsub connector.
You can see rvbuilder2002 entire post at:
http://www.vansairforce.com/communit...radio+transmit