Bigger is better for spotting is just another version of 9 vs 45. It's probably true bigger is better but there is no switch between 7 and 30 where the bullets suddenly appear.
This video does a pretty good job of illustrating the major spotting issues.
First 2000 yard splash at the 1:00 mark.
The major issues are lighting, mirage, backstop responsiveness, and target responsiveness.
The lighting is great, full sunlight with the sun behind the shooter. This keeps the sun out of the shooters eyes and the plumes are the most visible.
The mirage is medium heavy, but they're shooting across a drainage that keeps the line of sight above the hot ground.
The backstop is steep, dry, hard packed, and vegetation is sparse. The best URSA target spots are on abandoned logging roads that have a layer of crushed rock road base. The opposite condition is playdough. Wet enough to make a chewy clay that gives absolutely no splash.
The target is an appropriate size for the range but small enough that it moves when hit. It was freshly painted before the string. We use 1/4" thick plates suspended from chains for our range. The plates are suspended with bolts located 1/3 the way down and maybe 1/4 the way in from the edges. This counterweights the plate against itself and makes it highly responsive. The targets are not readily accessible, so no hit indicators or painting between sessions. The worst condition would be an extremely heavy or hard mounted target that isn't regularly painted and doesn't have a hit indicator.
I have a range with targets between 1200 and 2300 yards about 30 minutes away. The NorCal URSA range is 75 minutes away. 10 years ago, I was shooting one of those ranges weekly. These days it's more like monthly. I've spotted 6 Dasher hits at 2200 yards. I've seen 6' dust plumes from my 6XC past 2000 yards at the URSA range and I've seen the same range eat 800 grain solids without blinking. There were four 50 cal guys there that day, all experienced 1000 yard shooters and one that regularly did well at that range. A few hours later, lighting improved, and the backstop had dried out enough to start showing splashes. The 50 splashes were probably just visible a half hour before the 30 cal.
The most intuitive spot is going to be from your rifle scope. Range and conditions can make it impractical, but this should be the opening case. There should be no "getting back on target". You need to develop some combination of rifle supports, weight, weight distribution, body position and gun inputs where the gun tracks consistently and straight enough to keep the target in the field of view. There are endless combinations, and I haven't seen a best for everyone everywhere yet. I started with a preloaded bipod on a squeeze bag. Today it's a Phoenix bipod, hard rear bag and adjustable bag rider. The bipod is on a welcome mat mounted on plywood with leveling feet. On flat desert terrain, a shooting bench to move the line of sight above the vegetation makes a lot of sense.
