Ogive Curve Help Needed

OK, so here's the situation:

I'm trying to convert an HO (1/87) scale locomotive into something like this:

Lehigh Valley John Wilkes Locomotive

The stumbling part for me is the streamlined nose. Gil's excellent tutorial on open petal nosecones gave me the inspiration I need. I would really rather use a petal design rather than a series of small truncated cones. I'm just weird that way… ;)

I only lack one thing: Namely, an elongated (not hemispherical) shape to scale to fit. Can I take a petal design for a half-globe (hemisphere) and stretch it vertically, or are there other considerations in creating an ogive that I'm not aware of?

Thanks in advance,