If you cant get it just right , get a Vetus shaft coupler . It allows alignment to be several degrees off . I know of a boat with dual diesels and they had to be kept horizontal for lube reasons , two Vetus couplers allowed the shafts to exit at a down angle . Problem solved , but not cheap !

Vetus may be hard to find if you aren't in the Netherlands, so try Federal and there are a few others . Vetus is my personal choice .

BTW , I have a small Vetus coupler tucked away in the far reaches of my shop . I could be talked out of it . It was installed on an Atomic 4 and then "repro-ed" when the client wouldn't pay his yard bills , " no cash, no splash " ( in 12" letters over the shop door) . The one I have is good for minor mis-alignment and vibration control . I'll post the spec's when I find it and dig it out of the parts locker .