Size Modifier and Reach

Size Modifier and Reach is a set of rules on B402 describing how Size Modifier and Reach interact.
==Basic==
SM 	+1 	+2	+3	+4	+5	+6 	+7 	+8 	+9 	+10
Reach	0/+1 (C)	+2	+3	+5	+7	+10	+15	+20	+30	
===Grow===
B58 Growth:
:Increases in SM affect your arm and leg length when calculating reach and determining whether you can negotiate obstacles; see Size Modifier and Reach
===Stretch===
B88 Stretching refers to using it, increasing "effective SM" of a body part WITHOUT increasing "overall SM" of a body part (ie making it easier to hit/see)
Unlike Long Arms (B53) this has no bonus to swing damage because "no extra mass or muscle".
*Though interestingly: being a high SM does not give a bonus to swing dmg (they're just expected to buy more ST).
Stretching only refers to increasing "reach" via stretching arms. Logically stretching legs should increase the reach of kicks but only "negotiate obstacles" is mentioned for that.
Stretching neck should also logically increase reach for bites / headbutts but only "see over barriers" is mentioned.
===Diffuse===
Later notes about a Swarm occupying a hex could imply an SM+4 modifier per B414 Attacking an Area aka Targeting a Hex
==Powers==
P76 referred to by Kromm below is Small Size and Combat which highlights the importance of relative SM.
Relative SM importance is already present on B402 but not emphasized on B19.
Applying P76's "relative" to B19 for example means while SM0 is -1 to hit SM-1, SM+1 would be -2 to hit them, while SM-1 would be at NO penalty to hit them.
==Limit FOUR==
Below, Kromm suggests capping the maximum bonus or penalty possibly at four.
==Kromm==
:29 May 2008:
What people actually find baffling is:
#The absence of SM from Melee Attack Modifiers (p. B547), which is simply a case of us missing something in a summary.
#The absence of a note on relative SM, which is on p. 76 of Powers.
#The absence of a limit on relative SM in the previous ruling, which is the only house rule here. I like a limit of ±4.
== Sound ==
There are not rules for sound generation (for example can larger SM creatures inherently make more noise than small ones).
==Zombies==
GURPS Zombies 108 specifies that this bonus to reach does not benefit bites, that it "affects arms, not teeth"
402 actually only says "you have a longer reach with your arms" so RAW it wouldn't increase the range of knees/kicks/slams/headbutts.
A lot of players probably assume it at least increases kick reach. Stretching refers to stretching legs after all, but then 
There is a Long Legs trait which CAN do that though under Extra Legs. B55:
:increases your effective SM for the purpose of calculating reach when kicking
For some reason it's worth the same value as an enhancement even though it doesn't boost swing damage. Probably because of the 2nd benefit ("and when clambering over obstacle") which arms don't give
Stretching can increase Neck length which presumably SHOULD increase the range for bites/headbutts, but if normal SMAR doesn't help then it probably shouldn't here too.
==see also==
*Small Size and Combat
Category:Rules
Category:Tables