What cams/rpm range are you planning for ? Is it a daily driver ?

Reason being excessive spring pressures really beat up valve seats, also think about your valve guides and compatible materials with the valves. Titanium retainers are cool , but wear quicker than stock or the crower chromoly ones. The Ti retainers allow for an extra 200-300 rpm before valve float. Just some things for you to think about.

I myself like to drive my car and the thought of a retainer failing makes me sick.