Except for the speed, there should be no other restrictions (if not mixing with single/dual ranks):
For quad-rank memory modules:
• One memory module per channel supports up to 1067MHz.
• Two memory modules per channel are limited to 800 MHz, regardless of memory module speed.
Page 124 of the Hardware Owner's Manual:
http://www.dell.com/support/Manuals/us/en/19/product/poweredge-r410
Also, with BIOS version 1.1.5 (almost 4 years ago), support was added for 16GB DIMM's, raising the maximum memory for the R410 to 128GB. This specifies dual-rank, so it is unclear whether quad-rank 16GB DIMM's would also be supported, but the speed decreases likely still hold true.
http://ftp.dell.com/FOLDER00792842M/1/PER410-011100BIOS.txt
http://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_poweredge/poweredge-r410_User%27s%20Guide8_en-us.pdf
http://i.dell.com/sites/doccontent/shared-content/data-sheets/en/Documents/R410-SpecSheet.pdf