Wayne, I beleive the Abbey uses an Alko chassie so I have go the information directly from ALKO
When the Al-KO Group took over B & B Trailers in 1982, the standard practice for the fitting of brackets for the arm of a 'blade' type stabiliser to a caravan / trailer chassis 'towbar' members; (using Scott as an example); was by drilling and fitting an "L" type bracket. This required 2 holes to be drilled, one above the other on a vertical plane. Such a method of fitting was NEVER permitted on AL-KO chassis 'towbar' members. If such drilling has taken place, it is our recommendation that the chassis member be replaced.
Permission was given for 2 holes to be drilled, providing they were on a horizontal plane and neutral axis, in the centre of the towbar member. This resulted in the introduction (using Scott as an example) of the 'A' type bracket with 2 horizontal fixing positions.
In preparation for the proposed introduction of EEC standards, AL-KO wrote to all stabiliser manufacturers on 25/02/91 making the following statement:-
From January 1992 the drilling of chassis 'towbar' members would no longer be permitted. All 'blade' type stabilisers MUST use a clamp or bolt-on bracket. If after this date drilling is carried out this will invalidate all warranties. As a result of this statement some manufacturers (Scott included) have produced clamp-on brackets, which have been tested by our R & D Division and have received AL-KO approval.
During this period, 1982-1992, a great many caravans / trailers have had the chassis 'towbar' member drilled, using side by side fixings, with no detrimental consequences. A few failures have been recorded; these have been traced to multiple drilling and/or towing with 'chassis based' vehicles. This type of vehicle has heavy springing (this does not include soft spring off road vehicles) but vans of the 'Transit' type and lorries, usually with leaf springs. Such springing can produce a heavy shock wave; placing undue stress on chassis members with forces it is not designed to accept and thereby could cause a failure.
Unless multiple drilling has taken place or the caravan / trailer is to be towed by a chassis based vehicle, the drilling of 2 holes side-by-side on an AL-KO chassis 'towbar' member was and is considered acceptable for the period 1982 to 1992. No problems are expected to arise although occasional inspection is recommended. After 1992 all chassis MUST use a clamp or bolt-on bracket.