I’m going to rebalance my entire portfolio to 80%VOO 20%VUG for a little more growth tilt but I have a question about maintaining that allocation

I’m not asking for personal finance advice just clarification on how the math would work

So as the title suggests I’m going to be doing this allocation over the next year or two. (Sell stocks in my taxable account next year once I get out the military cuz I will be in a lower tax bracket) my only question is how would I balance this allocation

I thought that I could do 100% VOO in my taxable and then in my Roth allocate that so that the combined allocation is 80/20 but eventually I will max out my Roth and keep putting into my taxable so wouldn’t that just dilute my VUG position ?

Should I just do 80/20 in both accounts or should I do 100% VOO in Roth and then the rest in taxable. I can’t seem to wrap my head around how to get it as close to that split as possible. I’m 22 and this is the first portfolio rebalance I’m going to do in the 3 years I’ve been investing.

Thanks in advance