I have some experience setting up the Customer master additional data fields in SPRO.

For the General data - additional data maintain via menu

Logistics General - business partner - customers - control define attributes

for sales data - additional data
Sales and distribution - master data - business partners - customers - sales

maintain reserve fields in customer master
 

Product Allocations

You maintian the product allocations in a sales info structure, via flexible planning.

The first thing you do is to create and SIS infostructure that will contain the product allocation + incoming orders for relevant products (SAP provide info-structure S140 as a basis for product allocations - easiest plan is probably to copy this & modify your copy as required)...

IMG > Logistics General > LIS > Log. Data. Whse > Data Basis > Info Struct.

Maintain After this you need to set up the ATP check in SD to check for allocations.

The IMG path for the SD bit is:

IMG > Sales & Distribution > Basic Functions > Availability Check and Transfer Of Requirements
Availability Check > Availability Check Against Product Allocation

Once these are set up, you assign your allocation procedure (defined in the customising step above) to the material(s) which are to be controlled through product allocation.
 

Beam Back -> SAP Cafe for Sales and Distribution