If I'm measuring correctly the Santana with octalink cranks is 190mm?
I'm looking at the FSA Mega-Exo here.
https://www.precisiontandems.com/

The FSA specs on their website list Q-Factor as 163mm.
Anyone installed these on a Santana (mine is a Team Scandium) and do the stokers cranks clear the chainstays?

It's been a few years since I replaced the bottom brackets on our Santana Noventa. As I recall when I did I found the BB's were significantly wider than typical for Ultegra cranksets. I assume that's so the stoker's cranks will clear the chainstays and also to provide the appropriate chainline for the 160mm dropouts.

Not all FSA tandem cranksets are compatible with a Santana, noting that Santana builds their tandems using a 73mm wide bottom bracket (BB) spec. vs. the more common 68mm width used by most other tandem builders.

Let's talk about the 73mm spec first, as that's pretty straight forward: Santana spec's the wider BB for two reasons. The first is to allow for the use of large diameter, un-dimpled chainstays and the second obviously helps a bit with regard to moving the chainline out 2.5mm to help off-set the 160mm rear spacing. Santana also added a special "far-out" front derailleur mounting bracket to their tandems around 1999 for use with a quill type front derailleur that also helps to off-set the chainline by moving the front derailleur another 5mm. FSA now offers a similar deal for tandems.

As for FSA cranks, purportedly there some FSA tandem cross-over cranksets out there that can be installed on either 68mm or 73mm wide BBs. However, not "all" FSA tandem crossover cranks were produced this way. On the sets that can go both ways, there is an extra set of 2.5mm spacers that are installed between the bearings and cranks on 68mm BB's, and simply not used with 73mm BB's. This same type of arrangement is used on certain models of FSA's road and MTB cranks as well. Therefore, before buying a set of FSA tandem cranks for use on a Santana you'd want to have the seller verify that the cranks they're selling are compatible with both 68mm and 73mm bottom brackets.

TandemGeek is correct. More specifically FSA MegaExo Aluminum cranks have the spacer and will work with wither 68mm or 73mm bottom brackets. See FSA's documentation on line for more information.

I have had no problem simply placing my a 113mm squared tapered bottom bracket and Davinci cranks on my 1993 Santana Noventa. Plenty of clearance on the chainstays. This setup gives my stoker her normal Q factor that she uses on her single of about 158. On her single she uses a basic Sugino triple crank with 113mm square taper. The only difference in the tandem and single setup in the BB on the tandem is a 73mm BB, however both spindle lengths are the same. I have not tried it but I suspect that the Suginio cranks would work well with a 73/113 bottom bracket as well at a budget price.

Precision's website list Santana in the description but no Q-factor spec.
The only FSA Tandem Mega EXO SETS I see on the FSA website are
speced out as coming with the spacers and going both ways.
If the 163 Q on the website is correct then it puts the stokers cranks dangerously close to hitting the GINORMOUS Scandium chainstays on this bike if I move them 13.5mm closer on each side.
Was hoping some one had used this exact setup problem free in my quest to get away from the current setup and on to external bearing that I've come to really like on my single bikes.
TG.
How is Precision to deal with?
Thanks all.

Mark Johnson has a wealth of knowledge, a ton of inventory, is a Santana dealer and has a great rep.

Pick up the phone and give him a call. That's always the best option for tandem stuff when it's not exactly a no-brainer component question.

I'm just in the shopping mode at the moment and did not want to bother someone if I wasn't buying right now.
The price he has those carbon FSA cranks for is very tempting however.