Memory_Limit adjustments

Hello all. I am using a form combined with PHP to upload files to a website directory. Worked fine until I tried to upload a file 1.7 mb in size. My php code isn't the bottleneck as I scan the file first and reject the upload request if it exceed 4096KB. So I looked at the php.ini file and tweaked some settings. Once I changed the Memory_Limit setting from 8mb to 28mb, the file upload without a problem. So, my question is, is the 28mb setting going to cause problems elsewhere on the server or is this a relatively modest setting? Should I adjust it further? The server is a Linux server running Apache 1.3.37 with PHP version 5.2.3. Current memory usage as follows: Current Memory Usage

             	total       		used       free
Mem:      21898120     283912   21614208
-/+ buffers/cache:    	283912   21614208
Swap:     0          		0         	 0
Total:    21898120     283912   21614208

Thanks for any help. --Rick