In my experience, the biggest factors regarding the effect of wheel and tire size on handling of a Sterling is probably the width of the front wheels and tires. You're right: Most owners have HUGE rear tires, but that fact alone shouldn't affect steering and handling much. The problem is up front where people (myself included) usually use wheels and tires that are way bigger than were ever intended for a Bug.
Stock Bug wheels are very narrow, front and rear. The rims are usually just 5.5 inches and the tires are usually 165 series or smaller which is just 6.5 inches wide. But the body styling of the Sterling is conducive to having rear wheels/tires that are far wider and bigger diameter than stock Bug, and front wheels/tires that are wider but about the same diameter as stock. Cosmetically, that's the combination that looks great. Functionally, having really big tires in the rear doesn't mess with handling too much, especially if the rear suspension is IRS (1969 and up). If anything, it might help make the car a tad bit wider and more stable.
On swing-axle bugs (1968 and before) wider rear tires can do weird things because the camber (top edge tilt in/out) of the tires changes a lot over bumps. As such, you can end up with a really wide tire that only contacts the road on it's outer or inner edge.
But the interesting story is up front. People buy wider rims and tires because it looks good. I am in this camp. I want my car to look good. (Derp.) But the wider front tires essentially put a longer lever-arm on the hub, which fights you with steering. Over bumps, it might jerk the steering wheel a little to one side or the other.
So to kind of answer the question, the ratio itself doesn't matter much. Just make sure the front tires aren't too wide. The sky is the limit on the rear.
On the front of my main Sterling, I think I have 215 series tires (on 17x7 inch rims if I'm remembering correctly.) In my opinion, that fills the wheel well nicely and doesn't have too much bump steer. But even that tire is ridiculously wide for what these cars actually need. Functionally, the front tires should be narrower than that.
Early on I used to read up on what Porsche was using on some of its cars. In terms of configuration, our cars are very similar old 911s form the '70s. I think a lot of them used tires in the range of 165-185. I just did a Google search and the info on multiple sites suggest that 215 is a VERY wide tire for the front of an old Porsche 911. Many of us are putting front tires in our cars that would be appropriate for a Cadillac with a front-mounted V8.
As a rule of thumb for the Sterling, on the front use the narrowest tires that in your opinion still look good. The car doesn't need anything wider than 165 series up front, but 165 series tires will look weirdly skinny in the context of the body lines. In the rear, do almost whatever you want. Fill that nice big wheel well.
As one other aside, I've found that it's actually quite difficult to find matching tires when you're using vastly different dimensions for front and rear. Most tire manufacturers have many different lines of tires but there is a limited number of dimensions for a given line. Add to this that most modern cars don't have a huge bias in tire size from front to rear, so there aren't many lines that offer big rear tires and smaller front ones. Large tire size differences in a given car is mainly seen in older sports cars and modern exotics which means those tires can be rare, expensive, or both. When you can find them, they are often sizes for old muscle cars with 15 inch rims. It can be a challenge.
