If the problem is that you have been supplied, either by a dealer or manufacturer, with a machine that you feel is unsuitable for the application, then whilst it remains the responsibility of the business operating the warehouse (the duty holder) to ensure that they are providing the appropriate machine for the application, you should check with the supplier to ensure that the machine supplied has been specified in accordance with your order. If ultimately you believe the supplier has not conformed to your order, then you will have the right to recourse through them.
The best advice that the FLTA can give would be to firstly contact SEMA, as it is their guidance and then refer to the Manufacturer’s Specification Sheet which will almost certainly provide the machine dimensions and the minimum working aisle width etc.
In answer to the critical question of whose responsibility it is to ensure that the machine is of the appropriate type to allow the deployment of best practice and therefore undertake the operation as safely as possible, then as stated previously, that responsibility will always sit with the duty holder.