[Plugin: Contact Form 7] Checkboxes – Controlling layout

I have 40 options people can choose from – and this number will grow.
Currently, they list one after the other, and look very messy in the page layout. Ive tried adding <breaks> br/ in appropriate spots, but this section of the form then fails to show.
Would love a pointer to some documentation that can help me with layout control.
Thanks Heaps.