"Need be" vs. "Needs to be"

I've written the following in a sentence, but now that I look at it, I'm doubting my grammatical instincts and wanted to get a second opinion.

...the balance need be swayed only slightly...

Is the use of "need be" here correct? I read this as essentially identical to:

...the balance needs to be swayed only slightly...

but I haven't been able to find any other written uses of the first syntax. Formal references for this usage would be appreciated, but more general comments are of course welcome. Thanks!

Both are fine. Need, like dare, is sometimes called a "semi-modal", in that it can be used like modals (eg can, may) but can also be used as a normal verb (eg like want).

So The balance need be swayed only slightly is parallel to The balance can be swayed only slightly (the meaning is different - this is just showing the syntax); whereas The balance needs to be swayed only slightly is parallel to The balance requires to be swayed only slightly.

I believe that the modal use is becoming less common, and I suspect it is altogether less common in US English than in UK, but I'm not sure about that.