Waistcoat Draft - looking for some advice please.

I'm a bit of a lurker on forums (I read posts but rarely ever comment or post).

I've practised drafting the coat several times using standard measurements and practised drafting the waistcoat once using standard measurements.

I was now intending to try drafting a waistcoat based on my actual measurements and herein lies my problem. I'm a touch on the "rather obese side" so standard measurements don't help me. I'm 5'10", my neck measurement is 18.5", my chest measurement is 52", and my waist/belly is 54".

My question is should I:

(a) use 54" as the measurement to work with and then add a dart near the underarm to pull the chest to the 52" measurement, as in the photo below? (Which would look something similar to the notes on the blog for a portly cut draft)

or,

(b) alter the side seam between the back and front to accommodate the 2" change similar to the picture below?

A while back I purchased a cheap waistcoat to wear with my sport coat. Because of my measurements, I had to purchase a waistcoat with a 56" chest to accommodate my stomach. To make it fit me better, I took it in underneath the arm. So to my mind, altering the side seam on the draft to make my own waistcoat seems like the best option.

Thanks in advance for any advice that can be offered.