I guess i just jumped the gun when i bought the step-up ring. I was a little to excited to shoot it and wanted a quick fix for the filters. Im ordering the correct 46mm filters today.
In case I came across as too harsh...
Be sure to keep your step-up ring.
There are some filters that you will use a lot. Those are the ones that you want to have in 46mm versions.
There are others that you may want to try on your TLR, and/or which may serve you well on other equipment, and/or which you will already have in the 52mm size.
Or others which are hard to find in 46mm or very expensive, and which you don't want to both two versions of - one for your 52mm equipment, and one for your 46mm equipment.
For all those, the step-up ring will be great.
I have a 65mm lens for my C330 (and my C220) which takes 49mm filters. I also have 55mm, 80mm and 135mm lenses, all of which take 46mm filters. A step-down 49-46mm ring wouldn't work on the 65mm lens, but a step-up 46mm-49mm ring will work on the other three.
Here is an example of how I approached the issue. I wanted to try some IR film in my C series TLRs, and needed an R72 IR filter. They are relatively hard to find, and fairly expensive. I wasn't sure whether I'd shoot a lot of IR, and didn't know whether I'd need to shoot it on more than one lens. As a result, I decided quickly - buy a 49mm filter that fits the 65mm lens, and keep the step-up ring handy if I decide to use the other lenses.
If I end up shooting a lot of IR, using a variety of lenses, I'll spring for the 46mm IR filter (if I can find it).
Matt