Advice on trap arm length

I am allowed to have a trap arm run of about 8' in 2", but my trap arm needs to be 10' to allow the sink to be placed where I want. Would you guys just go ahead and do it or would you try to plumb in a relief vent somewhere along the trap arm to offset any possibility of a venting issue? I have never had to run such a long trap arm before so I am hoping someone might have some experience with a situation like this. Oh, and this installation won't be inspected.

thx

With UPC Code, I'm allowed only five feet on 2"

trap

We were allowed 4 ft from where the waste pipe connected to stack to
to where trap connected. If this is just the trap under the sink you extend
up to 1 ft.

arm

4' here also, but just install the vent connection within the legal limit and pipe it back to the existin vent. If this is the only fixture on the existing stack, then "offset" it to the legal limit and then run the arm.