Replying to Tips on consistently locking in on rails?

So i do rails quite a bit. I can front 2 and I am learning back 2. I can only do them if I have a good slide and lock on good. What are some things to do so can get to the end of the rail every single time (besides going super fast)? My head wants to blame it on my non centered bindings but I know that's not true lol. I know I should look at the end of the rail.

Should I have my knees bent?
When I bend my knees should I try and keep my shoulders parallel to the rail (like the same angle, not like counterrotating or something)?

Any tips are appreciated. Thanks.