G,
Closing the gaps requires much determination but not much trial and error. The tape measure tool and the enclosed PDF will remove the trial and error.
In your case, when you removed the O72 switch (14.25") you were able to fill it in an O72 curve. You wanted to insert an 1.378" plus a O36 switch (10") in a 16.5" section of straight track which left you with 5.125" to fill. Can't be done with FT pieces. I find the enclosed PDF table useful in closing the gaps. It shows gap length and FT pieces need to fill it. If you examine the shortest gaps at the start of the table you'll see that all gaps are not shown. The smallest possible gap that can be filled is 1.375", the shortest FT piece. Next is 1.75"; then 2.75" (2 x 1.375"), and so on. You'll see that there are impossible gaps throughout the table though their frequency diminishes as the gaps get larger.
If you use the tape measure tool to measure the gap and consult the table you'll be able to fill most gaps. Sometimes the key to filling the gap is to make the gap LARGER as I had to do to fill the 1/8" gap you had. Your gap was 5.125", one of the impossible gaps. I moved the crossover 10" towards the bottom of the plan which made the gap 15.125" and fillable (11 x 1.375"). It would be possible to reduce the number of small pieces by judicious placement of the crossover farther (4.5") toward the bottom.
Gaps are not always in a straight line. They will also manifest themselves as a misalignment after coming out of a curve. In the case of a simple oval, the parallel sides are of different lengths. The key to fixing these is to turn it into straight inline gap. The first step is to join the misaligned curve to the side keeping the exit inline with the original track which will create a gap or overlap. Use the gap filling procedure to join the ends.
Jan
