[DanDan]

There is an underlying text in my Sticky. i.e. these measurements are difficult to interpret, and are best used as part of the overall jigsaw puzzle. A mode calculation just another part of the jigsaw. The question, 'where do I put my speakers and where do I sit to get the best compromise in my particular room' is a big ask. To fully answer that I suggest that we need to use all the tools mentioned working together holistically.

Pragmatic decisions will determine approximately where the gear goes in the room.
This will result in a range of possible locations for speakers and listener. The Room Mode calculator can show you some very dangerous spots to avoid. For instance it may describe an axial mode with a null expect around that 38% spot. A sine wave at or near the predicted mode's frequency will make this null audible, confirming the prediction. You will find the frequency is slightly different to the calculation. Two heads are better than one. Now that you are sure of the problem area, you can move speakers or/and listener back or forward. Measurement software will then confirm the best compromise. Note that the height of the speakers is just as important. They can be shifted out of a trouble spot by a height change, perhaps an inversion. Slightly up and angled downward can sometimes get out of the vertical null, plus help avoid comb filtering from the bounce off your console. Conversely you might want to place the woofer exactly in the null if there is another dimension equal to the height. It ain't easy!
DD