Anal safe diameter?

Quite new to dildos, I have an Njoy wand and can take the large end quite easily, some lube on my hole some pressure and rocking and in it goes
I recently got a rabbit from my wife (the ears stopped working so no good for her) and wow that’s nice ! Bit over 40mm dia and I love it again some lube and pressure and no worries I love the full feeling and stretch and love pounding myself
I am thinking about moving up a bit in size probably up to 50mm with some contouring
I do not want to harm myself in any way, now or in the future does this sound a safe size to go to ?
Any other thoughts/ suggestions? M(61)