What happens if you send a second gate pulse into the start jack of the Rene?
Does it re start? Does it stop? Does anything happen?
If I recall the Rene correctly you can send it a start pulse, and an additional one does nothing.
In which case (even if it restarts) then a track with the appropriate length and time signature should do the job without having to worry about it.
I also seem to recall (and this could be totally wrong) that simply sending a clock into Rene will start it.
So you could perhaps program a clock track with Hermod and sequence it appropriately for when you wish to play the Rene beside Hermod, and stop the clock when you do not.
This way you can manually program the clock pulses, and get a lot of interesting things going on…
But to be direct, I don’t think there’s a way to have the pulse to start only happen once without creating a track for this, and then muting it after it’s played and started Rene.