According to a lot of crawler and offroad buggy guys, the stock 27 spline flange doesn't cut it, so to make it last, they made it thicker.
Below is an example of the cross section of the stock 30 spline Toyota.
https://www.marlincrawler.com/transfer-case/parts-upgrade/tc-hilux/pattern-less-30-spline-heavy-duty-transfer-case-flange
If you notice they used to have a thicker version of the 27 spline...but don't anymore. I searched all over for it and didn't come up with anything.
However, for our cars, I still think the weak point is the stub axle and the half shaft.
For anyone wanting to run 930 CV axles though, would modifying this flange be any different than just using these adapters?
https://zcardepot.com/driveline/rear-axle/billet-aluminum-axle-adaptors-930-cv-240z-260z-280z.html