[Image: http://i.imgur.com/UKyngK7.png]
The two accessories I will be using are unenchanted with the following r3 reforges:
Grapple Shot Damage 2 Level
Grapple Shot Damage 1 Level
The test is simply using grapple shot with the grapple shot 2 level reforge and recording my damage until I hit the max 3 times, and then equipping the grapple shot 1 level on the other accessory slot and recording damages until I hit max 3 times again.
First test, r2 Grapple 773 Max, Level 2 Grapple Shot Damage Step R5:
[spoiler=1530 4590 Critical]
4155 Critical
1391
1500
4332
1161
4458
1323
4539
1089
872
4590
1127
4590
4546
4081
1530
4507
1530
1281
1530
[/spoiler]
The Grapple Modifier Should be 198% of 773, or 1530.54. The results make sense.
Second test, r2 Grapple773 Max, Level 2 Grapple Shot Damage + Level 1 Grapple Shot Damage Step R5:
[spoiler=1561 4683 Critical]
1316
1034
1561
4640
1161
1541
4437
1561
4683
1561
[/spoiler]
If the reforges stack properly, the modifier should be 202% of 773 or 1561.46. The results add up.
So what can we conclude from this test? Currently in Mabinogi NA, the grapple shot damage reforge stacks with other grapple shot damage reforges. Although we cannot be certain this applies to all skill modifier reforges, it seems likely.