SSL slow when using libpq.dll

Hi,

I'm using psqlodbc on Windows to perform a query that returns on the order
of 1 million rows.

I have noticed that, when the DSN is configured to use SSL, the query runs
very slow, like three times slower.

However, if I delete libpq.dll from the psqlodbc installation directory,
the slowdown in the SSL-secured query is much less (only about 10-20%
compared to the unsecured query).

I have tried several of the latest versions of the driver, and the same
thing happens in all.

Several doubts:

- I surmise that the absence of libpq forces the driver to use Windows'
sspi service to handle the SSL, is that correct?

- Is it normal that using sspi is that much faster?

- Is there a way, other than deleting libpq.dll, to force the use of sspi
on Windows when using the compiled distribution of the driver?

- Can deleting libpq.dll cause problems?

Thanks in advance,
Daniel Díaz