AntBauerS, I have used the Stew-Mac undiluted so far with very good results. It behaves as you would expect any other medium viscosity CA glue to behave. I wouldn't say it is any more or less stiff.
I also suggest that if you order glue from Stew-Mac, that you also order a sheet of Teflon Fret Slot Dam material from them. Just use the website search function to get it to pull up. CA glues don't stick to Teflon very well which makes it the perfect substrate to put behind a hole that you are trying to fill with CA. I just cut a strip to size and insert it into the stem, positioning it under the hole. Then, I take a small piece of card stock or a thin pipe cleaner and wedge it under the Teflon to hold it securely in place. When I am finished with the hole repair, the Teflon slides right out. I have never had an issue getting it out, and I feel it provides a better backing to the hole than a pipe cleaner with Vaseline on it.