This extract is taken from the PSG catalogue: Design for Large Movement.

We can supply non-standard designs of types ES07 to ES12 to allow for movements greater than Range 3 (+/-37.5mm).
For pipework applications with very large horizontal movements, the standard design of PTFE / stainless steel bearing with the large upper plate may not be practical. Large lateral movement could cause the pipe shoe to twist around the pipe, or a twisting moment can be applied to the pipe which is also undesirable. In these circumstances, it may be preferable to install the bearing with the smaller PTFE-bearing plate at the top. PTFE on PTFE designs with overlapping strips of PTFE can also be considered. Note that an increased coefficient of friction will apply for PTFE-on-PTFE bearings and a lower bearing pressure should be used.

For ES07 to ES12 bearings at higher temperatures, you need to downrate the load capacity by using the graph showing máximum bearing pressure on P136 of the catalogue.

Neither shape offers any great benefit, but a square, rather than circular, shape can be more economic as there is less scrap when cutting from a square sheet. The key factor is to ensure adequate surface contact area. Please refer to our catalogue for guidance on allowable bearing pressure, and take account of ambient temperatures since these will also affect the allowable bearing pressure.