The unladen height of my Witter detachable tow ball is 420mm. In contrast, the coupling on my Brian James twin axle trailer is only about 280mm above ground level with the trailer loaded and sitting level (and consequently zero nose weight). That's a heck of a difference and lifting the coupling this distance onto the tow ball is effectively trying to lift the front axle of the trailer off the ground and thus putting more load on the rear axle. When they are coupled, the tow ball settles some 20mm lower, i.e. it's then 400mm off the ground.

I discovered that Brian James can supply a 50mm spacer to fit between the coupling and the frame of the trailer but that still leaves quite a gap to bridge. The answer would be a tow ball that sat lower but none of the manufacturers give such dimensions. I know there are exemptions for certain high ground clearance off-road vehicles that would permit a drop plate to be used but I can’t find where these exemptions are defined and whether the FL2 qualifies. I certainly can’t find any adjustable height towbars for it. Do they exist?

One possibility might be the flange tow ball that Brink offer with a lower tow ball height than standard. Has anyone ever come across one of these?

EC Directive 94/20/EC stipulates that a vehicle in ‘laden condition’ should have a towball height of between 350mm and 420mm. The vehicle’s manufacturer could define ‘laden condition’ as ‘fully laden’. This is the maximum permitted mass of a vehicle as specified in the vehicle’s handbook.

A height of 385mm to 455mm is stipulated by the EC Directive if the trailer or caravan is in laden condition.

So it looks as if your FL2 is well within scope, the trailer on the other hand isn't. The 50mm spacer still means that there will be considerable downforce on the towball, fortunately you have 150kg allowance. Fitting a drop plate would invalidate the certification of your towbar - witter were very specific when I suggested that as a solution to the very low towball height on the Evoque.

Fit two Brian James spacers? Tangiers Orange - gone, missing her
Replaced by Ewok what a mistake - now a happy Disco Sport owner

Thanks, Andy. I realise that the Witter tow bar is within the limits set by the Directive and that the trailer isn’t but a slightly lower tow bar, but still within the limits of the Directive, would help. I’m not sure two spacers would work as raising the coupling that much would affect the run of the brake rods under the chassis of the trailer and I think they’d foul the trailer bed.

Another possibility might be larger wheels?

looking on the Brian James website the flatbed twin axle trailer is available with 10" or 13" wheels

So could be an option Tangiers Orange - gone, missing her
Replaced by Ewok what a mistake - now a happy Disco Sport owner

Thanks again, Andy. I’ve actually written to Brian James asking them if larger wheels would fit. The 13” would clearly be a better bet than the 12” ones.