Hiya mate, I'm not sure what the best way to deal with it in Reaper (haven't played with it for a while) but if memory serves....you should be able to bring down the track level by hovering the mouse over the top right of the track until you see the up/down arrows....then click and drag the level down so that it peaks around the -18 mark next to the fader control with the fader at zero. (you can adjust it on the fly while the track is playing). That should give you some room to play with but adding a trim style plugin at the top of the chain can also be useful to make sure you don't clip into the top of the chain.
There's another thread about peoples mix flows further down that might be worth the read as well.
- This reply was modified 8 years ago by Andrew Mckenzie.