Boost Performance Of S2Member?

First off, kudos to the team for a great plugin – unlike so many ecommerce/membership plugins, most of the features of S2M worked right out of the box. I was extremely happy how easy it integrated with authorize.net

Here’s my problem: I am running a combination of S2M – Buddypress – Buddyboss on Rackspace Cloudsites: http://members.skinnychef.com. Looking at the web page performance, time to first byte is excessively long (typically 8000-12000 ms) by comparison with other sites that I am hosting on the same server. See http://www.webpagetest.org/result/120616_8A_DT9/

I did read the thread at http://www.s2member.com/forums/topic/can-i-optimize-the-speed-of-s2member/

I am aware that I can speed up things by combining/minifying .js/.css, but that only reduces the number of HTTP calls – and from past experience with dozens of sites, I know that the first call is just taking way too long (reproducible with other pages, and over time). By the same token, tasks in the wp admin backend are similarly slow, at least 3-5 times slower compared to other wordpress installations I am running.

Here’s what I tried so far:
1. combined CSS from plugins into custom.css
2. removed plugins’ .css (per functions.php)
3. restricted loading of plugin .js only to pages where needed (per functions.php)
4. deleted any plugins that are not used (i.e. all plugins are active)
5. enabled quick cache plugin
6. tried plugin optimizer (little effect on speed tests below)

Here’s the result from speed tests for https://members.skinnychef.com/sign-up-for-200-calorie-fix-program?s2-ssl=yes

http://www.webpagetest.org/result/120616_8A_DT9/
all plugins enabled – time to first byte: 5.66 seconds

http://www.webpagetest.org/result/120616_HY_DVC/
Deactivated all plugins except S2Member, Buddypress, BP Profile Search
time to first byte: ~5.86 seconds

http://www.webpagetest.org/result/120616_V6_DWX/
Reactivated all plugins, only S2Member disabled – time to first byte now 3.82 seconds

Any suggestions?

No, you tried most of what I’d suggest…

It obviously involves s2Member, because when you remove s2 the time drops 2 secs, but I’d like to know if it happens when one of those two is added. Could you time these?

– s2Member alone
– s2Member and BuddyPress

First off, kudos to the team for a great plugin – unlike so many ecommerce/membership plugins, most of the features of S2M worked right out of the box. I was extremely happy how easy it integrated with authorize.net

Thank you for the kudos! :D