Split a 2 mod rare?

I understand how this works in theory, but I'm confused on how the split beast works with deciding what item to drop and what item stays on the altar when splitting even mod items.

I know that if you split a 3 mod rare the one that is dropped on the ground has 2 mods and is considered to be the "new item" for imprinting purposes. But lets say I have a 2 mod item ex. T1 %phys (prefix) and stun duration (suffix). Are there specific rules when you split an item with even mods which mod is dropped as the new item? Is it 50/50?

Would be best way of going about getting a duplicate of that single mod to:

1. Imprint single mod magic item
2. Augment
3. Regal
4. Split
5. If desired mod is on the 2 mod item drop that is not on the altar 50/50 annul the new item?
6. Use Imprint on old item with trash mod

If I follow these steps and get lucky with the 50/50 annul I should have 2 magic items with the same desired mod correct?

TLDR: Whats the best way to imprint/split beast to dupe a single mod on an item?