If he thinks your IWC Portuguese is a tad small, then I think buying a Patek will be a mistake. Which Portuguese do you have that he saw? The 7 day power reserve is a bit larger than the standard Portuguese chronograph. Something in the 42-47mm range is probably a good bet. That said, if I had $40k to spend, didn't want gold, and wanted to keep it fairly large, I'd look at:
IWC Big Pilot Perpetual in SS
IWC Portuguese Perpetual (the one with the double moon is 2mm larger than the standard perpetual I believe, but both are beefier than the Portuguese chrono)
AP Royal Oak Offshore Perpetual in SS (I'm not sure of the retail on this, or availability, but I've seen it pre-owned for well under $40k)
Some limited edition AP Offshore in SS.
The Patek Nautilus models I believe are in the 40mm range, and the Patek models that are larger than 42mm are few and far between, not to mention north of $40k.
If he likes his JLC Master Compressor, then another good alternative is a JLC Grand Reveil. It has some nice complications (perpetual plus alarm), is large, and comes in SS.