Not the most experienced lamping man on here but i took mine out with an experienced lurcher 5 or 6 times before i even slipped him leave him watch her run.
And maybe only slip the young dog on easy rabbits like squatters or leave him see the rabbit running for 2 or 3 seconds before you slip him.
I started mine at 8 months old so mine was a bit older id say hold him back a while just watching until hes a bit older .