It is possible to have a single timing point up to 16m wide using the RACE RESULT ground antennas, when placing one decoder on each side. You can match any combination of mat lengths (4.8m, 6m, 8.4m) to create extra wide timing points. 

If joining multiple mats in the middle with 2 different decoders you should ensure to leave at least 1 blank, or disconnected, antenna element in the middle section where the 2 mats join, this is because a transponder can only communicate with 1 decoder at any one time so this reduces the cross reads which occur.

If using an EU decoder then it is also necessary to set the UHF Channels to A/B for each system to reduce the interference between the 2 systems.

Find more information about this in this article about Combining multiple ground antennas and decoders