Mat/frame size for 24"x30" prints

I am thinking about having some color prints made from 4x5 transparencies in the 24"x30" size. Since I've discovered that matting and framing goes from expensive to outrageous when the 32"x40" mat/frame size is exceeded, I am wondering how prints this size will look in 32"x40" mats. Would they look better at perhaps 32"x38" or some other size that I could get out of 32"x40" mat board? I do like photos to have some space so as to not look cramped. I'm also wondering if it would be better to have the prints made an inch or so smaller.

I find that drawing some scale images in PS helps me work out what will look good(balanced). Also width of frame affects how wide the mat border should be. i.e. narrow frame needs wider mat border and vica versa.

I'd lay one on an uncut 32x40 first and see how it looks. You have 5" margins in the long dimension but only 4" in the shorter dimension. That would work okay if your in a vertical and optically centered, but for a horizontal I'd go 32x38 to avoid wider side margins.

A 24x30 print on a 32x40 board works for me. If you dont like two sides to be narrower than the others, you could always bottom weight the presentation.

In the past I always had 5" of card around the print. A while ago I dropped it to 4" (with a frame about 1.5" wide) because 5" always seemed too 'spacey' . I've just mounted some 36" wide prints and only left 3" round them, but the frames are about 3" wide, and visually I reckon these are much better as they dont rely on any card to 'big them up'.
It really is all to subjective though, and even after all the effort and getting things to look right there will always be someone who wants a dark frame to be light, or a different colour card or some other change!