I am trying to compare several different
configurations of webservers and app.

I am running with 25 users, each test runs
one silk transaction that contains three or
four formpost and also parses the html to get
sessions Id, etc.

Everything seemed to be ok, till certain configuration started giving a lot of errors
of empty session Id. I started reading the help to find out more about the problem, and
realized that according to the doc and the help the way I was running, multiple threads in stress test, by default silkperformer wasn't waiting for the formpost to end to send a new one, so in my last test it seemed that it was sending empty sessions id.
I ran it in sigle threaded mode, the errors are gone but the results are much slower than I expected. Is this right? Do this mean that all my other test are incorrect?

finally, what are the recommended settings for a test where the user has to follow certain steps (like in a shopping cart, where you have to select all the items before proceeding to check out, and then billing and
then shipping)??