Random Q: spacer size and side(s) f/ 2013 Cervelo R3 (BBright) w/ Gossamer crank

I have a 2013 Cervelo R3 with BBright bottom bracket standard. I currently have a 172.5mm Rotor 3DF and want to swap with a 165mm FSA Gossamer. The crank says BBright on the spider face (facing out) and has BB386EVO written on the backside of the crank arm. I know going from the Rotor to Gossamer is a downgrade but it’s temporary until I drop coin on a 165mm PM. Plus, I don’t race or anything so a lb won’t bug me. I can lose that from my midsection.

When I went to install the Gossamer, there was a ton of room after snugging up the non drive side crank arm. This lets me know I need spacers. However, how many, what size, and what side do they go? I know the BBright bikes come with the FSA Gossamer so was wondering if anyone out there can definitively tell me what size spacers I need?

Thanks in advance.

http://www.fullspeedahead.com/install-bbright-crankset-press-fit-30-frame-fsa-road/

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ive seen that. It’s not a gossamer and one would think it’d be the same but it isn’t. Mine sticks through much more so spacers are needed.