Gonna be installing my 5100's soon and will likely add the diff drop spacer kit at the same time. Been doing some searching on the net and most seem to be in the $25-35 range. I noticed that the RevTek brand stated that it will help extend the life of the factory inner CV boots. So my question is: Is that all this spacer kit is used for, protecting the boots? Is there no additional stress on the shafts if the spacer kit is not installed. Thanks.