Healey 3000's have that spacer also, it strengthens the stub axle, so you get less knock back on the brake disk pads on cornering.
I have struggled with the balance issue in the front of my TCS for some time, and finally bit the bullet and bought a hunter on car spin balancer off ebay. It really works nicely and I now have a vibration free Europa. I also had all my alloys converted to tapered lug nuts, to center the wheel. Note that just because you now have consistent centering of the wheels via the lug nuts, the wheel balancing machines at the tire shops still use the center of the wheel to center it, which of course, is cast off center on the Lotus alloys. When converting to tapered lug nuts, I should have had the machinist bore the centers true also.
Oh, and on wheel bearing adjustment, I guess I get a bit anal since the looseness of the bearings affects pedal travel due to pad knockback. So I tighten the nut as per the manual while turning the hub, insert the cotter pin, and loosen the nut until it is hard against the cotter pin. If it is too loose, that is, if you detect more that a slight movement with the tire on when at the 12 and 6 oclock positions, I remove the nut and machine off a part of the nuts surface that hits the washer. Then I try again, and iterate until I get the minimal looseness.
I also found out after many track days, that the red grease will minimize bearing wear. With the usual Hi-temp disk brake grease, the hub would get so hot the grease would cake and the bearings would always loosen up during the track day, but with the red grease this stopped all together. YMMV.
Jerry Rude
4005R