I'll grant you that on a plane which was REALLY designed for an inverted engine, they COULD have done something about the tank height from the start.

But that said, there's no real issue with the way things are now EXCEPT if you are not used to dealing with inverted engines.

As others have stated, all you have to do is get the engine tuned and make sure that you keep the throttle at idle or cut off prior to starting the plane, to avoid hydro-lock.

On most inverted I use a cut off or fueling valve that prevents fuel flow to the carb until I'm ready to start the plane.

Once you to to start the plane there is no problem what-so-ever.

No unreliable idle, no high idle, no overly rich mixture.

If the MINOR .5 to .75 tank height difference on an inverted engine were to be a huge problem, we could never fly our planes upside down, let alone pull uplines nor downlines.
In an upline the tank height difference of my Giant U-Can-Do is well over 8-9 INCHES, and it does just fine.

BTW: the pressure differential over that distance is not even measurable by all but the most highly accurate instruments...

I run a Giant U-Can-Do with an inverted Magnum 1.80 w/o any problems as well as a smaller one with a Saito.

The Saito comes so slobberingly rich out of the box that it is amazing the thing will even start....

I saw one guy chew up a full tank last week on an inverted 1.20, letting it idle for 3-4 minutes... he had not tuned the engine yet.
After I re-adjusted the engine, the fuel consumption dropped to the point it is now sipping fuel slowly.