...can't tell you what a bike is going to ride like based on one specific number from the dimensions...
I wouldn't get too wound up on that number either... or all this recent stay length battle across the market will have you selling that frame off as soon as you get it just from feeling "outdated"! esp. seeing how other production frames out there already go way lower than 15 and quarter, like Dobermann for example, or GMD's sick vanilla cream dream machine at 14.5 on 26's...
next we'll be seeing frames with a 14.18" bb height, claiming in magazine ads it will help you pop 360's on flat ground. Then someone will claim they hit the magic number at exactly 14.20.
Post up some pics when you get it though, I'd be interested in checkin' it out.
Quality tubes and welds will help it to last, but overall geometry will help you improve. If it feels weird you probably won't feel comfortable to push yourself.
Get something proven and try it out if you can... If you have to go custom... start w/riding something similar to your intended design. Think hard about the positive and negative effects that they design changes will make... just make sure it works for you.