It doesn't have to be all that huge. This is nearly the same exact scenario as Cell/Piccolo and Androids. Sure, Cell doesn't rival the Androids, but he definitely is rivaling someone who rivals them. I think these are near duplicates of each other.
The tightness of the gaps of 19/20 with Piccolo and the Super Saiyans makes things extremely difficult to make any of this work. I always felt by the way it felt and looked, it could be like this...
Vegeta 100
Goku 96
Trunks 88
Piccolo 75
Or something around there. But if you do that, then 19/20 end up impossibly low. Which isn't realistic. Honestly the 19 Pre to Super Saiyan Vegeta gap is one of the hardest chains to master in all of the series. I'll show you what I have for now and let's see if we can improve upon it. I'm willing to get creative here because it is the hardest in the series, but if we put our minds together perhaps we can get something good.
Super Saiyan Vegeta 1,250,000
Super Saiyan Goku 1,200,000
Super Saiyan Trunks 1,100,000
Piccolo 1,000,000
20 Post 850,000
Sick Goku 750,000
19 Post 700,000
Sicker Goku 600,000
20 Pre 550,000
19 Pre 500,000