No, the extra weight is not a problem. The wheel hub and seal design is. When you replace the cork (some do, some do not and use RTV instead) coat the cork in RTV before putting it in place. Leave the side of that axle jacked up over night to let the RTV cure without any gear oil creeping along. Assemble the next day.
The axle vent design is also...ancient. The spring loaded rubber gasket likes to stick and causes the housing to pressurize, helping gear oil go where it does not belong.
I recommend to replace the vent mushroom with a simple hose barb fitting, run clear tubing up to the frame rails with a loop in it to account for axle movement, and put a cheap in line fuel filter at the end that you zip tie at a convenient location at the frame rail. That way, the axle can breathe, you know the vent is water tight up to the level of the filter and it is unlikely to clog, ever.