I've also done that though, due to the tool not having much purchase on the hub it can slip, causing injury from the sudden release. Could try cable-tying it to the footrest to prevent it moving but it's best if it can be held onto the hub so, if possible I'd get someone to help, leaving you with both hands on the torque wrench.
I’ve never had a problem but always make sure the handle is nicely stable on the footrest before applying torque.
Regarding clutch tools, I just bought a new basket & plates for the Monster after discovering how badly worn it was. The seller included an alloy version of the bolt-on holding tool that looks like it might be a better option; I didn't try it as I used the old school tool but it looks to be an improvement over the plastic/shortbread version anyway.
