Brian is close regarding Classic Roadsters’ solution.
The provided a fiberglass weight box which holds 150 pounds of sand. It is mounted directly behind the grill shell. Top of the box is even with the top of the body side panels. It is trapezoid shaped to fit the body as it angles in towards the grill shell. It’s about a foot and a half deep and a foot long (front to back).
The weight helps, but the ride is still pretty stiff unless you soften the front end.
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)