Flanges on a pyramidal sheet-metal surface model

[cjjatpuresilica]

Recently rollupswx has been kindly helping me resolve a pyramidal sheet-metal model.

I have a residual problem that has been dogging me for some while; namely the flanges and in particular the bottom flanges on the attached model.

I cannot apply fillets to the intersections between the flanges and the main body without introducing rips.

I accept that I could thicken the surface model without the bottom flange surfaces and then add standard flanges under the sheet-metal option.

However, regardless of how wide I set the mitering gap under auto corner mitering, the end result always diminishes the very bottom of what I describe as the hip beams or corners.

It is imperative I retain the hips/corner beams in their entirety, thus my attempt via the rectangular cut-outs through the corners of the bottom flange surfaces in the attached model; which hopefully will leave the hips/corner beams in tact after filleting the intersection between the flanges and the main body.

So how do I introduce rips at the end of each of the bottom flanges to allow a radius to be formed?

Do I just form the rips by simple extrusions; or is there an automatic simpler means?

Or am I going about this in entirely the wrong manner?

Thank you for your kind help.

cjj@puresilica