Does anyone know how Impale chance works with cleave?

Lets say you have 80% impale chance with one weapon, and 100% chance of the other. Path of building will average the difference of your weapons at 90% chance to impale. Is that correct though?

Reading the wiki: https://www.poewiki.net/wiki/Cleave_of_Rage (and normal cleave) First off, Cleave makes two separate weapon attack roll calculations and then combines both into a single hit. It says that on-hit effects scale off the final hit, and also crit is rolled independently and if one weapon crits, then the attack is considered a crit. Does it work the same way for impale?

Essentially the question is: Is the impale chance with cleave* your best weapon chance, or an average of the two?

edit: did some research on cleave and other ailments and the best i can find is bleed: https://www.reddit.com/r/pathofexile/comments/6ond14/30_dual_strike_and_cleave_can_only_bleed_of_one/dkjtnp2/

For bleeding the damage/chance is rolled separately but combined into a final hit. However, he goes on to mention that things like stun it's a boolean yes/no. Impale is a debuff, so ailment information isn't necessarily relevant. However it could function similarly and roll the impale damage separately and so you have the "100% chance to impale but 20% chance to impale for half damage (5%)" essentially.