Simmons Bilt vs. Aero Half Belt sizing question

[hungapotamus]

I'm sorry to clutter the forums with another Aero sizing question but mine is very specific.

I have a Simmons Bilt jacket size 40 that fits well but I'd like my next jacket to be a T-shirt fit if you will. I just purchased an Aero 50s half belt (I think) that's a size 36 (!) but I had the seller double check and remeasure so it seems like it "should" work for me.

Simmons Bilt size 40 dimensions:
-Chest: 22"
-Shoulder: 18.5”
-Sleeve: 24.5”
-Back Length: 24”
-Front Length: 25"
-Bottom Opening: 20.25"

Aero Half Belt size 36 dimensions:
-Chest: 53.5 cm (21")
-Shoulder: 46 cm (18")
-Sleeve: 62 cm (24.4”)
-Back Length: 60 cm (23.6”)
-Front Length: unknown (1-2" drop?)

I can comfortably layer a sweatshirt under the Simmons Bilt and it feels like there's excess material under my armpits.

First - are these 2 jacket patterns even a good point of comparison?

Second - what do you guys think? Will the Aero work for me?

I can still cancel the Aero since the back length and sleeves were a bit off in the sales listing.

 

[Aloysius]

I think dropping sizes to get a slimmer fit is usually not going to get you there, like people who downsize the boxy Highwayman just end up with a weirdly-shaped jacket. You need a jacket that's supposed to be that slim.

Your jacket above is a CHP. If you get a slim pattern (like 1930s half belt or Premier Highwayman) in a 40, it'll wear slim. I don't think you can really compare across jacket types.

The pattern has much more to do with it than raw measurements, as I keep telling people here.

I have jackets with the same PTP where one is a shirt fit and the other can accommodate wearing a suit underneath.

 

[zebedee]

I don't think the sizing comparison will help, here. Pattern is the key.