Thanks so much Lucati,
I visit the eBay page that you point out above, and just in time to purchased the last switch available
By the way, I notice the thickness of this switch is only 3 mm, so a double 29mm banjo bolts might be too long, while the regular single19mm banjo bolts might be too short.
I wasn't going to post about this until my thread is up to date, but it looks like it will takes longer for me to completely update my build thread since there are so many things to transfer from my old build thread...
so here we go:
I plan to use Staubli Quick Dry Disconnect system and their banjo fitting is about 3mm thicker than your normal banjo fitting, so exactly the same added thickness of this switch.
and since you also purchase a lot of ProTi Titanium Bolts, you might already knew that ProTi offer a longer Titanium single banjo bolt with 21mm length.
But just in case you are not aware,...
so I purchased 1 pieces of this 21mm single longer titanium banjo bolt from ProTi to test fit, and it arrived a few days ago. (standard single banjo bolts length is 19mm)
(you might also remember that one "notorious so called resident expert" at the old forum with a forum handle name like a "medical procedure" 
claimed / posted on my old thread that he knew only 1 manufacturer IN THE WORLD that made a longer custom TITANIUM single banjo bolt that will work with the Staubli banjo and ask people to PM him so he can sell it to them 
)
Well, turn out, ProTi already make a longer Titanium single banjo bolt and the ProTi Part# is M10L21-OT03 link:
PROTI Fully Forged 64 Titanium Bolts, Panigale,S1000RR,RSV4
so we don't need to PM that "fakeDOC"
Here are 2 pictures to compare their length from 19mmvs21mm and 29mmvs21mm to better illustrate (the gold one is 21mm):
View attachment 387View attachment 388
The washer for Banjo application came in 3 sizes, 1mm thickness (stock Ducati cooper washer), 1.5mm thickness (most aftermarket cooper washer) and 2mm thickness (aftermarket cooper or aluminum washer).
I plan to use 1mm washer and for this switch application it will need total of 3 washers in total.
Again my Staubli banjo fitting total thickness is about the same as the combined thickness of a regular banjo fitting plus the switch fitting, so by using Staubli fitting, its thickness is enough to simulate the combine thickness of the regular banjo plus the switch fitting.
Now, let's try to use the double banjo bolts at 29mm length first. And assume we will be using 3 washers with the most thickest 2mm.
Since I only have the Ducati stock 1mm washer (well I have 2mm aluminum washers, but it is hidden somewhere in many of the boxes in my garage) so, I will just simulate this by using 6 Ducati washer with 1mm thickness instead
after all 3 x 2mm = 6 x 1mm, and below are the pictures of 6 washers x 1mm:
View attachment 389
Now I test fit it onto my Brembo Brake Caliper and as you can see despite using 6 x 1mm washer, the 29mm bolt is still too long as I can't tightened it to go in more,
and there are visible gaps between the copper washer even with 6 x 1mm stacks of cooper washer.
(by the way, I also just test fit using this double banjo bolts, Staublis banjo with 6 stacks of 1mm washer on both my RCS17 Corsa Corta brakes MC and stock Brembo clutch MC,
and the gap was even worse since both of the MCs has less thread than the caliper below)
View attachment 390
Now, lets use the slightly longer ProTi 21mm single banjo bolt instead and as you can see they threaded all the way in properly
,
so I am pretty sure the 21mm ProTi single (but slightly longer) banjo bolts is the best length for our application with this switch or with the Staublis:
View attachment 391View attachment 392
They are very very nice ! 
