It's not a disadvantage, Dave, if other (sonically desirable) aspects of the arm significantly outweigh the above (in reality, tiny) disadvantage, nor is it in any way a disadvantage having a detachable headshell when fitting a cartridge and/or quickly swapping from one cartridge to another!!
Moreover, it is certainly not a disadvantage when, in some cases, the sonically desirable aspects, mentioned above, enable the arm to outperform its fixed-headshell counterparts, as is the case when comparing the Jelco with, say, a Rega arm of approximately the same price, particularly if a low-compliance cartridge is being used. Which arm would best suit a DL-103, I wonder?
Remember that tonearms, just like everything else in hi-fi, are a series of compromises. Therefore, of far more importance is considering how well a tonearm matches the physical and sonic requirements of the partnering cartridge, than whether or not its headshell is fixed or detachable.
Interesting idea with the washers, Stephen. I'm glad that it's proved successful in your set-up. Perhaps a suitably sized piece of Sorbothane would work well with less well-damped headshells than the Oyaide?
Marco.