A good test is to fit a cable tie loosely around one stanchion and ride the bike hard to see how much travel is being used. The whole idea is to use most of the travel with say an inch or so left for emergencies. If you don't use most of the travel then the springs are already too stiff.The cable tie can also be used to measure rider sag.
Good info, Barry. Of course, if you have gaiters, you will need to remove them to perform these tests.
And speaking of gaiters used on the Type-248's, these bikes were not made for them, and as such, a specific gaiter was never engineered for them.
When I installed mine, I had the top of the gaiter up as far as it would go, and I put the bottom nice and pretty right over the top of the fork slider, where the dust boot formerly sat. (I thought it looked nice, that way!)
It was pointed out to me that on compression, the gaiter collapses, but once collapsed all of the way, the fork cannot compress any further.
The trick is, to pull the bottom of the gaiter as far down on the fork slider as it will go. This will expand the gaiter a little more, giving you that much more fork travel.

If I had a bike with a aftermarket fork brace with gaiters, I think I would remove the brace to allow more gaiter travel.