No personal experience but some things to think about:
-For some people, weed can make them sleepy and apathetic. You may try it and just not care about killing yourself or you may just straight up go to bed instead.
-You don't want to be inhibited enough that you fail your attempt. Like, you don't want to be so high you can't follow the steps correctly or have the coordination to do things correctly.
-Also, THC affects everyone very differently. The same weed can make one person relax and another person freak out.
I always recommend people do a test with their chosen method of subduing SI. Make yourself some tea a few days ahead of time and see how you feel.