After two days of intense work, I finally completed installing more than 180 Detail West code 83 railbars at 39 scale feet intervals. Lots of work, but visually rewarding. Can't wait to paint and weather the track now.
I decided to go against common advice and install railbars inside the rails and not only outside. It is widely believe HO scale railbars may cause running issues when wheels bump on them. In fact, I tested a few bars with cars equiped with RP25 profile metal wheels and found not problems. I fact, they do clear the railbars. In some very rare cases, the railbars were a little bit thicker. Using a hobby knife, I scrapped about 0.01" of material on the top to make sure no issue will never happen.
So yes, you can install, just like the prototype, railbars inside the rails. But be careful enough to test the track and cut off except material if needed to make sure you won't have problem in the future.