On my system, the hidden options do not work.
I mirrored a small local site <http://127.0.0.1/>
the number of active connections is 1 / when updating it is 1 or none
the displayed transfer rate is 5Kib/s
The log file :
HTTrack3.40-alpha-4+swf launched on Wed, 08 Jun 2005 17:40:16 at 127.0.0.1/

(winhttrack -qwC2%Pu65535%s%u%I0c32H0%kf2A150000%c100%f0#f -F "Mozilla/4.0
(compatible; MSIE 6.0; Windows NT 5.0)" -%F  -%l "en, en, *" 127.0.0.1/ -O
D:\aspiration2\a_csstestsalpha2,D:\aspiration2\a_csstestsalpha2 -%A
php3,php,php2,asp,jsp,pl,cfm,nsf=text/html )

Information, Warnings and Errors reported for this mirror:
note:	the hts-log.txt file, and hts-cache folder, may contain sensitive
information,
	such as username/password authentication for websites mirrored in this
project
	do not share these files/folders if you want these information to remain
private

17:42:51	Warning: 	* security warning: maximum number of simultaneous
connections limited to 4 to avoid server overload
17:42:51	Warning: 	* security warning: maximum bandwidth limited to 100000 to
avoid server overload
17:42:51	Warning: 	* security warning: maximum number of connections per
second limited to 5.000000 to avoid server overload
17:42:51	Info: 	Note: due to 127.0.0.1 remote robots.txt rules, links begining
with these path will be forbidden: /doc/, /zip/, /switcher.php (see in the
options to disable this)
HTTrack Website Copier/3.40-alpha-4 mirror complete in 22 seconds : 97 links
scanned, 96 files written (477177 bytes overall) [273697 bytes received at
12440 bytes/sec], 362023 bytes transfered using HTTP compression in 70 files,
ratio 35%, 48.5 requests per connection
(No errors, 0 warnings, 1 messages)

While I understand setting limits not to overload a server (if an ennemy just
wants to do it 10 instances will do it anyway), I do not understand why limits
apply to a local or private IP.
I don't usually mirror a small local site but much larger ones to check links
and find php errors.

Modifying Max tranfer rate, Max connections / seconds while mirroring still
crash Httrack without any message.
I didn't even try the 3.40-alpha-4 version online !