Hi, currently relisting from Auctiva does not allow editing, it just reposts directly (I am not sure even whether the listing can be subject of a relist credit if it sells on the second attempt).
Via Auctive is ok if a lower fee related aspect is NOT involved because you relist and revise the live listing, eBay will soon ask for more as necessary on a live revision.
In your case where a lower start price can mean a lower insertion fee you need to relist from eBay where they give the option to revise before the listing goes live again. (Update 25/06/07. On this point check out ninth_wave's and my next post below).