It's pretty clear when a player steps or jumps. So, if they do either of those with a runup and didn't mark back, it could be called a fault. Try throwing those different ways and I think you'll see it's clear.
Another option discussed at one point was simply requiring the player to complete their throw behind their mark. That provides similar benefits to those cited above but requires a rule change to allow jumping/stepping and releasing before landing on your lie. I'd be fine with that rules change instead of what we're discussing. One way or the other, we need to eliminate timing calls, the unnecessary 10m restriction and marking cost/effort, and allow throwing methods that help generate power and/or accuracy not available from standing still.
If there is no circle, then do you mean this for all throws? From the teepad forward? The momentum of those stronger throws (even a standstill drive for some of us) routinely takes one over (forward of) the lie as part of the follow-through. See here; maybe in 2/3 of these drives (backhands only, I think), the player has followed through forward of the lie:
www.bing.com
I personally would not advocate calling a foot fault on follow-throughs when the disc was released while the plant foot was in the lie. Not off the teepad, not in the fairway, nor outside the putting circle.
However, if you don't mean for *all* throws from the teepad onward, then where is the line/distance where one can no longer legally follow through forward of the lie? Even with a bigger circle than the current C1, it still has to be marked or measured.
I don't think getting rid of the circle is the answer. The PDGA has technical standards for discs and baskets. Maybe they should also for measuring devices. That's a vote for improving the no-magic, affordable rangefinder. Is there enough incentive for manufacturers to improve their current devices? Create new ones? Time will tell.
In the interim, we muddle through with the tools that we have...
I think this is a good discussion that will ultimately (maybe even in our lifetimes!
![Grinning face with sweat :sweat_smile: 😅](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f605.png)
) lead to a good solution. Indeed, an evolution in the sport.