Thats funny that you threw that in there about RJs and 500FPM, you dont miss an oppurtunity do ya!
If this were me, and plug it into the FMS and compare the info based on FL430 cruise and the new altitude. If it look ugly then maybe plug in LRC and look to see if that makes a prettier number. In any event im required to call dispatch in a situation such as this and it will be somewhat of a joint decision on what to do from there.