I might be able to assist with the connection you are refering to. However my tree is vast and I cannot attach or email it but should you be able to give the information you do have from your records I will place them and supply you with the section of detail applicable! As alternative supply an email adress and I'll invite you to my tree! Its on Ancestry.com. The downloaded gedcom file is about 15 megabites in size! It consists of around 8000 persons but obviously some are attachments to Slabbert/Slabbeart.
As far as I could find I have all Slabberts on record in South Africa since arrival there. However I must add that there might be (most probably are) some missing names and persons that are missing after around 1890 as most of these information is still not released publically! The once available on court records I do have!