Yes, there is. Add this to the bottom of each vest stage:
Code:
<modifier class="speed" value="-0.2" />
So that a full vest stage looks like this:
Code:
<carry_item key="tank_armor.carry_item" name="tank armor" slot="1" transform_on_consume="tank_armor_2" time_to_live_out_in_the_open="0.1">
<hud_icon filename="hud_vest.png" />
<capacity value="1" source="rank" source_value="0.0" />
<inventory encumbrance="1" price="1" />
<model mesh_filename="vest.xml" />
<commonness value="1.0" in_stock="1" can_respawn_with="1" />
<modifier class="projectile_hit_result" input_character_state="death" output_character_state="none" consumes_item="0" />
<modifier class="projectile_hit_result" input_character_state="wound" output_character_state="none" consumes_item="0" />
<modifier class="projectile_hit_result" input_character_state="stun" output_character_state="none" consumes_item="0" />
<modifier class="melee_hit_result" input_character_state="death" output_character_state="none" consumes_item="1" />
<modifier class="projectile_blast_result" input_character_state="death" output_character_state="none" />
<modifier class="projectile_blast_result" input_character_state="wound" output_character_state="none" />
<modifier class="projectile_blast_result" input_character_state="stun" output_character_state="none" consumes_item="0" />
<modifier class="speed" value="-0.2" />
</carry_item>