Thanks a lot for your comments Ian
From your marks some things become quit clear to me. For realistic reasons a 2 board solution will work much better for me.
1. The 5.5 and 6.5 overdrive sizes are in the sweetspot of the iS87 and compromises the 5.0 RS4
1. The 6.5 OD is in the sweetspot of the iS94, 7.5 at the edge of the sweetspot, 5.5 and 5.5 are (too) small with the iS94
If remarks stated above are true the iS87 will be the better option for me for the OD 5.5 en RS5.0 (maybe on the edge). I didn't try it's precedessor with a 6.5, but the 6.0 GTX worked very nice.
It appears to me that not very much has changed when you compare the sonic85 with the iSonic87, but this may be misleading while I don't know anything about the details. Which improvements may I expect on the water to feel and see (GPS) compared to the sonic85. I can imagne the differences might be small, but it is nice to know how 1 year development may work out
When I take a rough guess the best board option with an OD 7.5 is the iSonic101?
OK, thanks in advance. Time to go to bed now after a heavy thundershower woke me up in the middle of the night and made me put on the PC