Don't know if your Boomer is an HST or the 16x16 but have you looked at a stock NH rear remote kit? We have a TC40D & after looking at the options we added the 2nd & 3rd remote kits from NH. They come complete with every part (valves, pre-bent steel lines, brackets, levers, even the quick connects). They are definitely more pricy than other kits or piecing a system together; but the factory kits put everything where it should be.... bolts right on & an easy install.
We went that route because we wanted the levers at the factory locations for a clean install & intuitive function control, everything sits right were it should...
I didn't really look into it but check out NH part - DIA KIT, REAR REMOTE CONTROL VALVE #2 - HST - MT20117326. If I'm reading that kit correctly that is a factory NH 2 Rear remote kit for an HST Boomer 50. Around $1200 - $1300 but includes everything for 2 Rear Remotes to be installed as Factory... Just make sure you double check to see if I was reading it right...
Just an idea to look into....
Below is a pic of how clean the factory kit installed on our TC40D....