Main bearings will be fine with a .50 grind as bearings are under no real loading as such unlike bigend bearings
The nitrided surface on most of these cranks goes to around .25 to .30 so once ground beyond that you will lose the hardened surface.
Personaly I would not use a crank ground to .50 on bigend journals unless it was a naturally aspirated engine with a linear loading.
Tried this once before on a close to 350bhp car and it did not last to long, I've seen a few failures on cranks ground beyond the .25 so if I'm honest it's a risky game your playing there spike
In association with
Torque Of The South Motorsport
Nissan Performance & Tuning Centre
Forge Engine rebuilds to specification
Body Restoration, Fabrication, Repair
Paint refinishing facilities
Ecu re-mapping-Performance upgrades
Auto Diagnostics, Injector cleaning
Race & Suspension setup
General Servicing, Mots, tyre fitting
Full workshop facilities