DSF

i have a order for 4 large t-shirts the customer is very big so to speak (4XL) He wants a breast logo of his dj name and a set of headphones, simple! yes but how the hell do i work oyt here to put it and what size? Normally i do a breast logo about 3inch i just dont know where to place this one on the t-shirt

i would go just below the armpit sleeve and down from the highest part of the shoulder

I always align with the collar.

If you think about it, the collar is pretty much in the same place left and right on everyone regardless of size.

I usually have a sample 4xl t-shirt in stock and will get the customer to hold it against himself and mark the position with tape. Then when the order comes in I use this as the position that the customer agreed on.
But failing that I agree with what the others have said.