You may have different B+ with the SS rectifier in there, you'd have to measure. I think a 5R4 is a somewhat lossy direct heat rectifier, and a 5V4 is a not so lossy indirect heat rectifier. Don't have a tube data book in front of me to confirm. One thing with SS rectifiers, if it doesn't have a delay the voltage available at turn-on will be higher than it would be with the tube rectifier. If you have any caps that aren't rated for the voltage spike you'll find them the hard way.