Hi, Madlegs, I got this to work on my site, i´m using the Five template.you can adjust the with ass you see i have set mine to 88 %.
/* button full width DO NOT DELETE*/.sqs-block-button .sqs-block-button-element { display: inline-block; width: 88%; height: auto; padding: 1em 2.em; color: #fff; background-color: #272727; border-width: 0; font-family: "Helvetica Neue",Helvetica,Arial,sans-serif; font-size: 12px; line-height: 1em; font-weight: normal; font-style: normal; text-transform: uppercase; letter-spacing: 0px; text-align: center; text-de