I would have to recommend the saddle I have, an older Nelson Pessoa. There is nothing about it that is specifically wider or anything, but I feel very secure in it. I have a very pear shaped body, and my butt would make J-Lo run and cry in shame, but I have found that if the saddle fits your leg, as long as you bum doesn't hang off the back, you should feel secure. I ride in a 17" saddle, because I have short, stumpy legs, but I am not hanging off any where, and the saddle fits me and my horse. I have found that a narrow twist is what I prefer, and if you get into a wider seat, you may end up with a wide twist, which can be quite uncomfortable. Also, don't be tempted into buying an 18" saddle just because you have some junk in the trunk, saddles are measured more by the length of you hip to you knee than your bum. When I was first looking at buying a saddle, I thought I wanted an 18" or so seat, but ended up really liking saddles that are 17" or 17 1/2". Trying them is the key. Good luck in the saddle search. I got lucky and found the saddle I wanted online, used, dirt cheap in less than a week of shopping. I love my old used Pessoa, and I take care of it so it will last me many years!
On a different topic - Maybe you ladies can give me some ideas... are there particular brands of jumping saddles that made you feel more secure with your womanly figure? Clearly a larger seat size is in order, but is there something you liked or disliked about a brand? I noticed some describe a "wider seat" with a narrow twist, did they prove better for you?