i also bought some day abo some bellows. i also used a makro lens and wanted more.
my bellows are m 42 and so i had to buy some adabters to try all my lenses.
my last intension was the best i mounted my rodagon enlarber lens.
there are some formulas to look for the best lightmetering.
for example: ([used bellowlength / focal length)+1]² = the factor to be multiplikate the exposurtime.
a very good way to learn is a digicam (dont hang me ).
same advantages as a pola fast and low quality
very helpfol is mirror lockup and a cabelrelease