No idea on where to go around there, but for spaniards I've always used about 30cm of 86lb Amercian Fishing Wire single-strand stainless wire. Use a haywire twist to a swivel at one end and to a solid black ring at the other. You don't need more that 30cm as that will clear the sharp bits! You can also buy the traces premade but it just costs more that way. Get everything in black so you don't attract the fish to your terminal tackle instead of your lure! Won't help with sharks but I've never been bitten off by a mackerel. The short single strand is far less detectable to the fish than a metre of multi-strand which I have seen people use.

We spent 9 days up there over the easter break. we did a day on Mac Attack, and fully bagged out. we did travel some 250kms though.

the skipper of Mac Attack said no one had caught any mackies in shark bay within the last 6 weeks, FYI. There were a lot af very big boats/tow rigs up there over easter, and the filleting tables were regularly busy but I did not see any mackies or tuna getting slabbed up. there seems to be good numbers of mackies from Kalbarri south, so maybe the water is a bit warm past there. the Denham sound waters were a bit green tbh, which they often are, but i rarely fiond macks in dirty green water. 

 trip to steep point. When you leave the bay and enter ocean start trolling north along the fault line with deep diver lures (with single strand wire trace) in the 20-25m depth up past black rock on west side of dirk hartog island then turn around and head back south again.  Keep doing that you will pick up spanish mackeral, shark mackeral,   and we got some big wahoo there last year as well. (dont go too far north along dirk hartog island - if the wind comes in quick it is a long rough trip back south to safety of the bay) We also found nice yellow-fin tuna up to 15/20kg if you head out to around the 40 - 60m depths west of there using same tackle.  Of course check wind and swell before you go as it can get really nasty quickly when you leave the bay at steep point and enter the ocean. May is great time to be there so i think you will do well if weateher permitys cheers

 trip to steep point. When you leave the bay and enter ocean start trolling north along the fault line with deep diver lures (with single strand wire trace) in the 20-25m depth up past black rock on west side of dirk hartog island then turn around and head back south again.  Keep doing that you will pick up spanish mackeral, shark mackeral,   and we got some big wahoo there last year as well. (dont go too far north along dirk hartog island - if the wind comes in quick it is a long rough trip back south to safety of the bay) We also found nice yellow-fin tuna up to 15/20kg if you head out to around the 40 - 60m depths west of there using same tackle.  Of course check wind and swell before you go as it can get really nasty quickly when you leave the bay at steep point and enter the ocean. May is great time to be there so i think you will do well if weateher permitys cheers

 Was up at monkey mia over Easter and saw a bloke filleting a 21 kg mackie at the table, was really thick. He said he got it on a floater out the back and was near the last nav marker out around the sand bank. Also saw about a 20kg cobia too getting filleted up. Both monkey mia side. As Dave said never know your luck with a floater out. 

 Definite thumbs up for the floating bait, and a rigged gardy instead of lures. I reckon sometimes you need to vary the size and type of your lures as well. Hope you have great trip anyway.