Assist Power's increase in power will only acknowledge stat boost when said stats are at level +1 or above.

Stats drops are factored in, Assist Power's base power decrease by 20 for each stage of stat drop but will ignore stats that have dropped at level -1 or below.

The highest base power Assist Power can achieve is 860, to test this I used a Smeargle (103 SpAtk) and a Bronzong (364 SpDef).

Smeargle's moveset:

_Acupressure

_Tail Glow

_Spore

_Assist Power

Tail Glow first to immediately put Smeargle at +6 SpAtk in two turns, then Acupressure until Smeargle can't boost its stats anymore.

Then I used Assist Power against Bronzong and here are the damages:

194 - 180 - 200 - **176** - 200 - 178 - 184 - **202**

Since there are 7 stats (including accuracy and evasion), max power is 20 + 20 * 42, which is equal to **860**.

Stats drops are factored in, Assist Power's base power decrease by 20 for each stage of stat drop but will ignore stats that have dropped at level -1 or below.

Smeargle (103 SpAtk) vs Gardevoir (265 HP / 228 SpDef)

Code:

Smeargle: +6 SpAtk
Damage: 96 HP
Power: 140

After Gardevoir's Captivate

Code:

Smeargle: +4 SpAtk
Damage: 51 HP
Power: 100

Smeargle (103 SpAtk) vs lv 59 Magnezone (159 HP / 123 SpDef)

Code:

Smeargle: +6 Def
Damage: 45 HP
Power: 140

After Magnezone's Mirror Shot

Code:

Smeargle: +6 Def
-1 Acc
Damage: 47 HP
Power: 140

After Magnezone's Screech

Code:

Smeargle: +4 Def
-1 Acc
Damage: 34 HP
Power: 100

After Smeargle's Cotton Guard and Magnezone's Mirror Shot

Code:

Smeargle: +6 Def
-2 Acc
Damage: 44 HP
Power: 140

Assist Power's increase in power will only acknowledge stat boost when said stats are at level +1 or above.

Smeargle (103 SpAtk) vs lv 59 Magnezone (159 HP / 123 SpDef) second test

Code:

Smeargle: +3 SpAtk
Damage: 64 HP
Power: 80

After Magnezone's Screech

Code:

Smeargle: +3 SpAtk
-2 Def
Damage: 60 HP
Power: 80

After Smeargle's Cotton Guard and Magnezone's Screech

Code:

Smeargle: +3 SpAtk
-1 Def
Damage: 70 HP
Power: 80

After Smeargle's Cotton Guard

Code:

Smeargle: +3 SpAtk
+2 Def
Damage: 93 HP
Power: 120

EDIT:

http://www.smogon.com/forums/showpost.php?p=3071599&postcount=1225

It seems this was overlooked ^^'

**Pumice Stone**

Concerning the item Pumice Stone:

_it cuts in half its holder's weight;

_combined with the ability Light Metal, it effectively divides by 4 the Pokémon's original weight.

Pokémon used:

_Machamp

_Entei (198 kg / 436.5 lb)

_Rayquaza (206.5 kg / 455.2 lb)

_Metagross (550 kg / 1215.5 lb)

**First test:** Machamp (394 Atk) using Low Kick vs Entei (434 HP / 295 Def)

*w/o Pumice Stone:* 168 HP dealt (100 bp)

*with Pumice Stone:* 123 HP dealt (80 bp)

**Second test** (to see if Pumice Stone has a modifier /2 or /3): Machamp (394 Atk) using Low Kick vs Rayquaza (321 HP / 192 Def)

*w/o Pumice Stone:* 149 HP dealt (120 bp)

*with Pumice Stone:* 122 HP dealt (100 bp)

At this point we know the the Pumice Stone divide by 2 the weight of its holder, but what about Light Metal ?

**Third test:** Machamp (394 Atk) using Low Kick vs Metagross with the Light Metal ability (364 HP / 394 Def)

*with Pumice Stone:* 112 HP dealt (100 bp)

Now we know as well that it stacks with Light Metal as well (and presumably with Heavy Metal as well, but it's rather pointless).