How do people do their own RDNS without a full class C ?

[Patrick Thomas]

I have a rack of computers collocated at a datacenter.  I do perform my
own DNS on my own DNS server, BUT, I do not have an entire class C of
addresses - I only have 64 addresses.

Therefore, my collocation provider says that I cannot do my own reverse
DNS.  I cn do my own forward DNS, of course (which I already am) but since
multiple people are using the class C block, the RDSN requests need to go
to the collocation providers name servers.

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THe problem is this:  I make frequent and manifold changes to my DNS, and
it will be a major pain for both sides (me and my provider) to have to
keep communicating changes for their DNS.  We would all be a lot happier
if I could administer my own RDNS.  But it is too late - they have
already assigned the other parts of the class C block to other customers,
so we are sort of locked in.

The questions:

1. Are we missing something ?  Is there some very elegant and easy
solution that ISPs generally employ for solving a problem like this, or
does every ISP customer with less than a class C have to rely on someone
else for RDNS resolution ?

2. Let's say there is no way around this, and that they really do have to
do RDNS for me - we thought that maybe I could maintain correct RDNS
entries in my name servers and that the ISP could just do a zone transfer
from my name servers - a zone transfer of only the RDNS records, and thus
get accurate information in an automated fashion from name server that _I_
control.  The problem is, my ISP thinks that the only way they could do
this is by wiping out their entire zone with my entire zone - apparently
there is no way to simply append my RDNS info to their own using a zone
transfer.  Is this true ?

They suggested maybe I set up some files to be appended and we do a `scp`
copy using cron to append the info to their name servers.  This is a good
idea, but it seems like a hack.

Any other ways out of this conundrum ?

Help and suggestions appreciated.  Thanks!