Darn, in the middle of converting an S3 and ran out of 3mm LEDs. I see I can fit a 5mm into one of the ends.
This may be a silly question, but would there be a problem? Would this 20mA 5mm clear LED in my hand run as cool and fine as my last 3mm in the other end of the loco? The 5mm is about the same physical size as the present bulb so fit will not be an issue.
As long as you can center it in the front headlight lens and it won’t be protruding through the shell, it should be fine. The size of an LED shouldn’t make any difference in regards to temperature.