-P, Short.

Cap,capped.
Hap,happed.
Hop,hopped.
Stop,stopped.

Weak -B (short).

Blab,blabbed.

-V, Long.

Crave,craved.
Grave,graved.
Rave,raved.

-F, Short.

Huff,huffed.
Cough,coughed.

-M, Long.