Modifying 26 spline extension housing to 30 spline

So I am looking to save some weight and money in my transmission build. I have 2 C-13386 extension housings (Aluminum overdrive 26 spline) and one C-99126 (Iron 1:1 30 spline). I would like to use my 30 spline main shaft with an aluminum extension housing (I'm going to use a 1:1 gearset). It looks to just be opening up the bearing and seal bores.

Has anyone modified a C-13386 to accept a 30 spline tail shaft bearing/seal? Has anyone measured a C-13212-2 or C-13305 (Aluminum 30 spline) vs. a C-13386 to see if the external dimensions are similar? I can get internal dimensions from the iron extension housing, but don't want to thin out a wall too much and risk breakage down the road.

Thanks for any and all help.