almost copy of post on KA Sail...

Hello,
I am looking for advice to chose a second hand SDM mast for my Koncept 5.8 from 2007. I am recreational windsurfer and will maybe use it 4 times a year in west Sweden in 25-30kt winds. I don't see the need to buy a brand new mast and I don't find that many KA used mast around here...nor see any sail... My two bigger sails 6.6 and 7.8 are S-type and share their gold north 4.60. In Goteborg it is pretty easy to find north, simmer, loft and pryde on used market, Swedish northsails distributor is close by and NeilPryde and simmer store a bit further. By experience the northsails masts have a specific shape, would it fit to Koncept from 2007? I understood the pryde don't have the proper flex, but since the simmer are compatible with north and north sails compatibility mast chart is giving the KA Sails compatible...what do you think? what brand and model should I chose. Do you have good idea to find second hand KA mast in north of Europe? I found a Northsails Silver 400 close by, good to give it a go? Otherwise should I take a 4.30 mast or a 4.00 + extension, the sail is given for 4.30 mast luff?
Thanks for your help and looking forward to rig this beauty, which receive so many appraisals for it's speed, control and light feel.
Best regards,
Plettil