Basso Diamante 56 vs De Rosa SK 54 stem & spacer sizing

[Leviathan]

Im looking at a new De Rosa SK but they only have it in 54cm frame size, and Im keen to replicate the fit of my current Basso 56cm frame which seems really confortable

I have a three part question (!)

1) Is there an online "stem & spacer calculator" where one inputs the frame Stack & Reach, ht angle, spacers and stem geometry, and it outputs stack and reach to the bars? Bikegeo.net doest really do that as you cant start with stack and reach, have to put in the whole bike geo and for example I dont know the BB height for both bikes.

2) If not can anyone confirm my rusty trig:
a) My Basso frame has Reach of 392,20mm, Stack of 566.60mm, Ive got 30mm of spacers including the "confort kit" and I have a -6 degree 110 stem so the bar location i have calculated is 620mm Stack, 500mm reach from BB
b) The De Rosa in size 540 has a 389mm reach and a 550mm stack so between spacers and stem Id need 111 mm of stem reach and 70mm of rise? Hence something like a 120mm stem at -6 woud require only 16mm of spacers

The ST angles on the two bikes are identical and I like to push the saddle tip quite far forward anway so I dont think that will be an issue

Like I said, a calculator would be helpful but if anyone can confim that I can replicate the fit with this new bike frame Id be thrilled. Have I missed anything??

[cyclenutnz]

I'm happy to say that, yes, I have made such a calculator. https://app.velogicfit.com/frame-comparison

I need to get De Rosa updated but the SK Pinnafarina is the same Geo as the 888 SK so that will serve for this comparison.

You would be better served to go for a 56. The 54 will require a full 45mm spacer stack with 120 stem (we'd usually take that config as a sign the frame is too small)

[Leviathan]

Indeed, the 56 would have been my choice but it wasnt on sale fr 2200 Euros like the 54 was at crc. Sadly it will have to be a pass, thanks for your help, 5cm of spacers is a no-no! .