user.rb

class User < ActiveRecord::Base
  
  belongs_to :plan # or however you get your plan - mine is actually not in an AR model
  
  def can_do_cool_thing?
    plan.can_do_cool_thing?
  end
  
  def can_do_other_cool_thing?
    plan.can_do_other_cool_thing?
  end
  
  def whatever_size_limit
    plan.whatever_size_limit
  end
  
end