Since we all know by now that Penny is the next harem girl,here's how you can get 5 lust points with her until the current update (Merry Christmas if the dev adds more ways to get lust points for her in 6.1)
1) When you go to hex A2 to meet the aliens,make sure Penny is with you.Choose the option related to huge mammoth dongs when talking with the alien couple.
2) Meet Penny at the pool.
3) Scout the hex B1 with Penny and win the fight against the Inquisitor leader.Before that,you have to make sure that the MC is not baptized or he didn't go through the cock canonisation process.Your combat and strength stats should be 8 or higher.
4) Know the location of Red Canyon from Marnie in the bar and then date Penny.
5) Enjoy her titjob service in the strip section of the bar on a Monday.You can know about strip service from Marnie.
6) After Melania puts a bounty on MC's head,there will be a day when the bounty hunter intercepts him.Make sure Penny is your scout partner(I would recommend rolling back to the exploring Trumpf City part in the afternoon once you find the hunter intercepting you and then saving at the map so that you can change the scout by loading that save if Bella is your partner instead of Penny).Then lose the duel against the hunter (firearm stat should be low).The Mar-a-gogo scene will trigger and after MC returns to base,Penny gets impressed at how MC handled the situation and she gets a lust point.
If you knew all these steps already,its fine.Just a fellow game fanboy trying to help.
P.S.: Steps 2,3,4 and 5 are strictly related to getting 4 lust points for Penny.You can choose either 1 or 6 for the 5th lust point.The other step can be used for Bella which could be of help once Bella is a harem girl in future.