change layout on check-out

On the checkout page the invoice and shipping address is displayed in two columns, but that does not fit very well inside my 3 column template. The border of the shipment address field is expanding into the next column. See attachment.

Could perhaps:
1) not include visible border or
2) Make the two address fields more narrow (my prefered solution)

I have a strong feeling that there is a easy solution to this, but I have not found any postings on this matter so I ask the forum for help..

Do you have any solutions to suggest?

If any are interested in the same, I changed the front end CSS file to the following:

/* checkout address layout, 24th june changed checkout address width from 700pixels to 100%, adress left and right from width 350px to 50%*/
.hikashop_checkout_address{
clear:both;
width:100%;
margin:auto;
}
.hikashop_checkout_address_billing_only{
clear:both;
width:100%;
margin:auto;
}
.hikashop_checkout_billing_address{

}
.hikashop_checkout_address_left_part{
width:50%;
float:left;
}
.hikashop_checkout_address_right_part{
width:50%;
float:left;
}


This seems to work fine.