IIP3 Calculation of N-path (N=4) Mixer

Hi,

I'm trying to calculate IIP3 value of an 4-path Passive Mixer (circuit given in the figure below) 

I've few queries:

1). Which simulation is best for this purpose? (according to online tutorials, there are several approaches available: hb, qpss with hb, qpss with qpac)
2). Should I use ports for all LO frequencies or only one?
3). When I'm placing ports on all LO frequencies (4 LO with 25% duty cycle, and 90° phase shift), and trying to simulate using qpss with hb analysis, the "Total number of harmonics" is equal to 117.649k (which is huge no.) due to which the simulation is taking a very long time (screenshot attached below).

4). If there a tutorial available to achieve IIP3, P1dB, NF of n-path mixers, if yes please let me know.

Regards
Arpit