If you allow me to comment on this:

Whether a portable implementation is possible or not is one thing (and
doesn't have to be a show stopper), but it is quite another thing if
the specification cannot make any guarantees in order to allow at
least non-portable implementations on most existing and future Schemes
(which, in this case, has to take nanboxing into account).

Am So., 25. Okt. 2020 um 21:41 Uhr schrieb Emmanuel Medernach
<xxxxxx@gmail.com>:
>
>
> Le 25/10/2020 à 20:32, Arthur A. Gleckler a écrit :
>
> On Sun, Oct 25, 2020 at 8:44 AM Emmanuel Medernach <xxxxxx@gmail.com> wrote:
>>
>> Ok for me to withdraw as it makes no sense.
>
> Do you mean that it makes no sense because a portable implementation is impossible, or for some further reason?
>
> So far as I regret it we could put it on hold, because a portable implementation is impossible, undermining its general utility.
>
> Emmanuel
>
>
>