Altering the arm hole on a sport coat

[JBrew]

I just picked up a new RLPL sport coat on ebay and while the overall fit is good, the arm holes are a little too tight under the arm pit. Everything else fits (shoulder, chest, lenght) but I'm curious if I can reasonably have the arm hole enlarged slightly. It would only be at the bottom as the tightness is only noticeable in the underarm. My question really is: Has anyone tried this in the past? Is this a workable alteration? How expensive is it, if it can be done? Am I better off going a size up and then tailoring down the chest, waist, etc?

Thanks for your help in advance.

 

[Despos]

Depends on how tight it is and how much needs to be let out to be comfortable. There should be enough outlet to widen the armhole about 1/2" on each side. Other things like shoulder slope or the position of the armhole could be contributing to the tightness. Narrow sleeve head could make the jacket feel snug in this area too,