Have you figured out Light Grenade yet?
Nah. I just used the standard 2x gap for that one. One thing it's interesting is that Cell says if he absorbs Kamiccolo, his initial stage evolution will be always complete, possibly referencing his imperfect form strength needed to absorb the androids. When he was finished absorbing the humans, he said he "overdid it a little" and got carried away iirc. This may imply he absorbed more than needed for the first stage.
If we assume absorbing Kamiccolo would be an addition like thing, then it could be that Cell (post humans absorptions) > Cell (1st stage complete) >= Cell (post weighted Kamiccolo)
I've it as
Cell 530,000,000
Kamiccolo (weighted) 667,000,000
Adding them up, it'd be 1,200,000,000 pretty much. Let's say his 1st stage completion he envisioned was 1,300,000,000... And the part he got carried away and overdit it, 1,500,000,000... Where I've him, 2x unweighted Kamiccolo and 17.
You see the light grenade as what, a 3.5x multiplier?
Edit: the first stage likely meaning the power he lost when he regressed to an egg and waited for 4 years to hatch.