How to have Noise independent of Image Size

Hello, recently bought Filter Forge after using a trial.

I've just run into a problem, basically I am using filter forge to create a series of procedural height maps for a game engine. These heightmaps need to be at varying sizes (and aspect ratios) and now I have realised the noise nodes I am using seem to be tied to the size of the image, however what I need is for them to not scale across image size.
For example, an image at 64x64, 128x128 or 1024x1024 would be showing noise at the same scale and is simply cropped at smaller sizes.
I've managed to get this working at larger image sizes by decreasing the 'Size, Pixels' setting in the Filter Library to compensate, however now I need to create lower resolution images and I've found I cannot make this setting smaller than image size.

tl;dr this would work if I could give a 64x64 image a 'Size, Pixels' setting of 253 but I am unable to do so. Does anyone know how to make noise scale independent of image size?

Please let me know if what I am saying is not clear.

Cheers,
Jira

@emme this seems to be exactly what I need, thank you so much!