multiple instances of unetbootin

I use unetbootin on a regular basis to write a with SUSEStudio built Live ISO (about 4GB) to an USB Stick and then I test it. Very often I need to write more USB Sticks with the same ISO and I would like to do this in parallel in order to speed up things (4GB takes 10-15 minutes to write on a USB Stick).
So I tried to open a second instance of unetbootin during that the first one is already writing an USB Stick. The second instance opens ok, sees the second stick ok but when I am starting to write it detects some already present temporary files which the first instance is currently using. I get a dialog asking me whether I want to keep the files or overwrite them. If I use the option not to overwrite the files sometimes it works ok, so both USB Sticks are ok at the end. However I had at least a couple of times the situation that the second USB Stick was not having the correct files.
Question: can you maybe use in the name of these temporary files the current ProcessID so that these files do not mix between more instances of unetbootin? I think that should be the easiest.
More exact what I want to achieve: to be able to write two USB Sticks at the same time using the same ISO and using two separate instances of unetbootin without caring about conflicts, files which may mix between instances and so on.
Thank you in advance!