This is a set of letter supports with a track joiner. With the letter and joiner the support is 64mm high under the track. This works with the current bridges I have purchase but you should check for bridge ramp height or supports. You can scale the letters to support a different height.
Measure your current bridge support height
The letters are 60mm high and the joiner base plate is 2mm or 4mm. I based this height off a Thomas bridge I have which is 64mm but others have 62mm. A discrepancy of a couple millimeters should not be a problem.
I recommend no more than 10% infill. These are still very string at that level.
Print a joiner for each letter and join with epoxy or glue of choice. Keep an eye on the direction of the letters as you glue the plate to them.
Joiner plate options
There is a 2mm and 4 mm joiner plate option for small discrepencies in your current bridge.
Still not quite right, then scale
Don't scale the Joiner, just the letters if your bridge is a different height. You want to scale only by the X and Y axis. Leave scale of Z as 1, assuming you are printing these as the STL has them oriented with the letters facing up.
- Measure your bridge height in mm
- ((your_height - 4) * 1.6 = scale %
- if you are using slic3r then this would be that percentage / 100. i.e. if the scale % was 93 then the slic3r scale is 0.93.