Well it seems I might be in the minority, but I would not propose to a woman who did not truly know who I am. Now ofcourse at this point you have to deduce how much of a lee or ler you truly are, but if it is a significant part of who you are, like it is myself, then you are not being honest with your future spouse, and while I would still not say this is immoral, I would say that you have to seriously consider the repurcussions of not being your true self with someone you are obviously considering as your life partner. Let me at this point tell you, that apart from being a 'ler, I am straight as they come, and when I brought up my fetish to my SO, she did not give 2 shits, she was just glad I was honest with her.
From this point out it is your call my friend, I just wish you good luck with any and all you endeavours.