You Won’t Believe This ― Far Wall Boasts.
There are 180 linear feet of wall on a doubles court. The striker is entitled to 150 feet of wall to shoot at. The opponents share 30 feet of “safe” wall; back third of each side wall.
(Figure 605)

The position of the ball is kept the same as for most figures in the previous posts looking at Rule 5 and boasts. A sweet spot can be found on the far side wall as was done in Figure 602 in the second post in the series.
You may have missed the significance of Rule 5 a iii. Here it is again.
Allow either opponent to play the ball to any part of the front wall or back wall and to that part of each side wall in front of the red floor service line.
The focus here is still on the last part about the side walls.
Most boasts are directed to the near side wall. Boasts to the far side wall are less common except for a shot to either front corner.
What do you think? If the striker requested a let would you, as referee, grant a let for any of the 5 shots shown above?
According to Rule 5, shot #1 is not interference. Yellow has cleared behind the short line. It seems pretty clear in Rule 5 that the entire left side wall ahead of the short line must be clear for the striker. Except for #1 all the other shots appear to be interference. By the rule they are all entitled shots. However, there is fine print which you will not find in Rule 5.
Shot #2 would not reach the front wall fairly. That removes the entitlement. Players are not entitled to shots that would not reach the front wall fairly. The referee again, just as for the near wall boasts, must make a judgement as to whether a shot would have reached the front wall fairly. It takes experience for players and referees to have a sense of which boasts will be good and which are doomed to failure. The next step here is to check out which shots, at least on paper, would be good. Find that sweet spot.
Far Wall Boasts ― Sweet Spot
Check Figure 605 above. Can you see shots #1 and #2 would not make the front wall fairly? Those are removed from the following figure. The interfering player (yellow oval) was removed as well. Otherwise, the angles are carried over.
(Figure 606)

With the reflected flight paths drawn in, it is clear #3 shot is not good.
The sweet spot is about midway between “C” and “D”. Which is roughly the midpoint of the full side wall.
Just as a reminder, as the point of striking changes, all the angles change and the sweet spot shifts as well.
Where would the defender be safe and not interfering? Anywhere behind the path of shot #3 looks safe. The entitled part of the side wall shrinks from 2/3 to about the front half. If the opponent cleared to the side wall but in the front half, he would be interfering.
It is critical where the ball is when a let is requested. On paper the ball is fixed at a point but on court the ball is moving and sometimes very fast. The referee has the tricky task of trying to pin point where the ball was when the let was requested. The referee has the additional task of pin pointing where the offending player was at the moment the let was requested. Plus, the referee must assess if the striker was ready to play the ball and requested the let at the proper instant.
The correct time to request a let varies depending upon the type of interference as described in Rule 5. Generally, the correct time is the moment the interference occurs. Here ball flight is the interference of concern. Ideally the striker is ready strike, and the ball is there to be struck. That is the moment the striker holds up on the shot and requests a let. The timing is important.
The referee must know when to take that mental snapshot. That is why the rules are very clear that a let is only considered when a player properly requests a let. Physical gestures may get the attention of the referee, but the request must be audible and at the moment of the perceived infraction.