[Brownie]

I retained the stock hammer spring because I felt the long one was WAY to heavy a pull on the long stroke.

The hammer spring is already compressed so your long trigger stroke is not working against the hammer spring at this point of the pull but rather the Trigger Rebound Spring.

I had read that you can keep your old spring to get a lighter pull.

This is true. It should be striking with roughly the same force that it was before. Remember that this was the same spring that was sending the hammer forward just fine with V1. The only real difference is the two part hammer but that shouldn't effect this.

I took her to the range today and she was hitting the primers way too light. Only popping off 1 round every 2 or 3 tried.

Something obviously doesn't sound right with this. Did you change anything else? What ammo are you using? One thing I would do is to remove the firing pin and make sure there's no greasy build up in the firing pin channel. Clean it out really well and refrain from oiling it when reinstalling as the oil will act as a dirt magnet. Personally I would strip the pistol and reinstall the LEM kit. Maybe something is out of kilter and a reinstall will get it right.

I assume a firing pin spring is in order (this guy: HK Spring | HK FPBS - HKPARTS.NET) but I wanted some clarity first.

You can change this if you want to but it's not going to make a difference as far as the light strikes go.