Damn it. I was all set to go with a .358 STA and then I read this post on WSM wildcats, which got me to thinking I better check those out first.

Who has done a .35 caliber on the WSM case. Photos? Loads? Speeds? Pressure?

Isnt that the 35 Wapiti?

I thought it was the 35 Sambar.

this should get you started:

http://35cal.com/ruger77_350wsm.html

I think they are the same but I am open to being wrong.

I say go for the 358 Yukon by www.z-hat.com
A standard length shortened RUM case that will duplicate the 358 STA

A mate runs a 35Sambar built on a Ruger WSM action. Literally 50-80fps behind the 358Norma with all bullet weights. A very handy cartridge.
Cheers...
Con

Nice to see you are able to get bigger bullets into the casemouth without splitting the brass. I'm going the other way: 300RUM necked down to .30 on a 30-degree shoulder to a .30-06 length in a 300WSM chamber which will be rechambered to fit. The 300WSM shows as having a .555 lower datum diameter while the 300RUM shows as having a .550 diameter. I have measured some of my own 300WSMs that have been fired and reloaded several times. I measure .552 and .553 at .200 above the casehead. I think I can use my original chamber and may not need to cut the breech end of the barrel...

The 338 and 358 WSM in the picture are actually made from 325 WSM brass and they are made using a plastic hammer and a suitable bullet only .The 9.3 mm , 375 and 416 are made from 300 WSM brass necked up with a neck expander

I have never split a neck reforming a WSM or WSSM case .I also neck up the 375 RUM to 416" and 458" without any problem