It is best to not have completed all Quarry missions or will not be able to retract the Hydra wheels as doing so will also skip the mission. This slows down the Hydra.
Despawn raidius of Quarry missions: https://imgur.com/a/b8uPO1e
The execution was alright, but the setup unfortunately had a mistake as the Hydra was not parked very well, which caused CJ to spawn to the left instead of the right (costing about 3 seconds). Despite this, the end of the run was so lucky that I decided it was a satisfactory time/result.
The GTA:SA community has been deteriorating over a long period of time. Many top runners are not currently present on the leaderboard. This issue has not been seriously addressed yet, but an attempt will be made to remedy it now.
As of this news post, the San Andreas leaderboard will function in