At a second look it looks like the 6N16B can take 300 volts if cut-off, so It should be just fine as is, I was more worried about warm-up time when it hasn't began to draw much current, but I bet it wouldn't hurt anything, these are tough little tubes
I really like these tubes, very linear and rugged. Probably the closest to a easily acquired submini 6SN7 (functionally) that you're likely to come across. I've used them for a handful of preamp duties and they work very well at a 185~ volt supply for small signal stuff. ~5k plate resistance, so something like ~12-15k plate resistor.
This is also a fine tube for use in a mu follower (or even morgan jones style "beta follower") and will be very nice paired with a mosfet follower to drive cables, larger loads, etc.