Looking for sforzando assistance

I don't know whether Plogue sforzando is something supported here or not. Does anyone know? In case this is the right place, here is my issue. If not, you can ignore.
 
I recorded samples of my old upright piano and am using something called SFZ Designer to build an sfz file for it, which I am triggering in SONAR using Plogue sforzando. But I'm getting double strikes for every note. It's like it's playing each sample twice in quick succession. Does it matter if my samples are .mp3 files, should they be .wavs instead perhaps? I opened the .sfz in a text editor and everything looks straightforward
 
When I open the .sfz file from standalone sforzando, the note seems to be striking many times very quickly.
 
Here is the sfz file that is striking twice:
 
// Title:
// Author:
// General Settings
ampeg_attack=0
ampeg_decay=0
ampeg_sustain=0
ampeg_release=0
ampeg_hold=0
ampeg_delay=0
// Group 1: 50-70
// Velocity Layer 1
<group>
volume=0
pan=0
transpose=0
hikey=70
lokey=50
pitch_keycenter=64
seq_length=1
lovel=0
hivel=127
// user opcodes
<region>
sample=..\..\..\Zoom Import\E4Loud.MP3
seq_position=1
 

I have a lot of experience with the sfz format but not specifically with sforzando.
My experience is all players have quirks and some even crash on some commands.
 
I assume what you sent is only part of a larger file, because the group command only
makes sense if you have multiple regions. Also, what you sent will only sound
between note numbers 50-70. So possibly the same sound is being
called up multiple times in overlapping areas.
 
There is a lot of unnecessary stuff, too. I can imagine the round-robin sequencer
may be confusing sforzando. Reduce your file to the basics:
 
<group>
hikey=70
lokey=50
<region>
sample=..\..\..\Zoom Import\E4Loud.MP3
 
Also, consider putting your samples together with your sfz file and change the reference.
 
sample=E4Loud.MP3
 
This is just so if you decide to move your sound, everything will move together.
Otherwise you move the sfz file and it won't find the sound files anymore.