Pxelinux can do a lot of things, but loading the solaris installer is not one of them. For that, it is easier to use pxegrub. What can you do if you still want to use pxelinux as your primary network bootloader? You can easily make an entry in your pxelinux.cfg/default for pxegrub!
First of all, here is what my /tftpboot directory without the many linux, bsd, and solaris boot files:
If you are paying attention, you'll notice that pxegrub's filename is different than normal. You have to end the filename with a .0. If you don't, then pxelinux will not load it properly, which caused me a bit of confusion. Also, you will need to place pxegrub's configuration, menu.lst, in /boot/grub at the root of your tftp. Pxegrub looks there by default.
If you have everything set as so, you will be able to load pxegrub from pxelinux with the following clause:
It's really that easy.