A decent idea Chad.
I thought that a qualifying distance such as 150 m could be the first round. That would thin out the group and yet allow everyone interested to have a go. Anyone can have a great day so even casters that wont cast over 200m can be involved and may achieve to the next level. IT could be that only ten qualify to move on and have another three casts. (I agree that first distances are retained). The next round could be a final or if many have qualified another cut off could be 180m.
Then I guess there will be a handful for the final three casts. Could be that their first cast remains their longest and that cast could win it.

I did win Vetrans casting at the Nats one time and had another second so I do understand how this may help.

Just my thoughts.