ZX6 2000 rocker cover gasket

After doing the shims a few months ago the rocker cover is leaking at the front left.
I put sillicon where it says to, thats not where its leaking anyway.
Didnt use any gasket goop, I guess the rubber has gone a bit hard and isnt sealing properly.
Should you usually replace this gasket, or just put goop on it?
Will find out what it costs and how long it takes the shop to get in stock, but if its something stupid will the goop do?
Pulling it all apart now to do over the next few nights.
I put sillicon where it says to, thats not where its leaking anyway.
Didnt use any gasket goop, I guess the rubber has gone a bit hard and isnt sealing properly.
Should you usually replace this gasket, or just put goop on it?
Will find out what it costs and how long it takes the shop to get in stock, but if its something stupid will the goop do?
Pulling it all apart now to do over the next few nights.