As long as both sides agree that the percentages are OK, you're fine, as long as:

(a) You VEST EVERYTHING (including your own shares)

(b) You know how you'll legally handle control after one of you leaves

(c) You have a serious conversation about responsibilities, one that confronts all the ways you can see things not working out; at this stage in my career if I was doing this I'd turn that conversation into a simple, bulleted MOU

(d) You remain observant about what the equity split is doing to morale. Frankly, sales of a new product is very hard, and it's more likely that vesting and termination are going to be your problems, but if they do really well, you need to remember that, again, sales is hard, and you don't ever want to lose someone who can perform in that role because they think they're getting an unfair deal.