Ok, how's this for an idea? Since Personal Lts. are at level 1 for effectively 4 levels, and their Vitality doubles once the party hits level 5 (assuming I can do maths right) they would be hitting 200% of their initial Vitality score. Over the course of the first 4 levels, would it make sense to increase their Vitality by 25% each time the party levels up? 125% at TL 2, 150% at TL 3, 175% at TL 4?